
Class ^xQ, \W 



Book 



__ 



Copyright N°_ 



COPYRIGhIT DEPOsn: 






INFECTION, IMMUNITY 

AND 

SERUM THERAPY 



In RELATION to the INFECTIOUS DIS- 
EASES which ATTACK MAN ; WITH 
CONSIDERATIONS of THE ALLIED 
SUBJECTS OF AGGLUTINATION, 
PRECIPITATION, HEMOLYSIS, ETC. 



BY 

H. T. RICKETTS, M.D. 

Instructor in Pathology, University of Chicago 



CHICAGO 

AMERICAN MEDICAL ASSOCIATION PRESS 

IO3 DEARBORN AVENUE 



I906 



LIBRARY of CONGRESS 
Two Conies Received 

APR 6 1906 

jf\ Copyright Entry 

AjjLc/ttqcj- 

CLASS CC AXC. No. 

/ 3 3 76^7 

COPY B. I 



^ 



R,* 






<? 



CorruiGHT, 1905. 

BY 

American Medical Association. 



PREFACE 



Immunity, in its present state of development, 
with its manifold new terms and special methods 
of experimentation, is a subject which appears dif- 
ficult to one who has not studied the newer litera- 
ture assiduously and grown into a knowledge of the 
conditions through actual work in the laboratory. 
Much of the literature is technical in character and 
appears in journals not commonly found in the 
hands of the physician and student. Much of it 
also is comparatively recent, and its "essence" has 
not yet appeared in books which are in general use. 
The literature of immunity, moreover, grows so 
amazingly that the analysis even of current works 
is a task of no mean proportions. 

At the same time, the subject is one of great 
interest and importance, and there exists a gen- 
eral wish, frequently expressed, to know more 
about the recent advances and the conditions which 
have operated against the success of serum therapy 
on a broader scale. 

The editor of The Journal of the American Med- 
ical Association, appreciating the need which 
seemed to exist, requested the writer to prepare a 
series of articles on the subject of "Immunity," 



iv PREFACE. 

which should present the general principles and 
the important theories and facts, in as simple a 
manner as possible. These articles appeared from 
week to week during the year of 1905 in the jour- 
nal mentioned, and after revision, and with such 
additions as would contribute to the completeness 
of the work, they are now collected, in larger type, 
in the present volume and under a more suitable 
title. 

It was thought best to treat the subject broadly, 
to begin with the fundamental principles of in- 
fection and resistance and to introduce the reader 
to the more complex conceptions of the present 
time by taking him briefly over the main historical 
and developmental steps. 

It will be obvious that the views of Ehrlich, 
concerning the production of antibodies, the nature 
of the reactions into which the latter enter, and the 
methods by which bacteria produce disease, have 
been utilized extensively. This course demands 
no justification, when it is appreciated that by 
no other means can one at the present time corre- 
late a multitude of well-established facts which 
hear on the problems of immunity. Whatever may 
be the eventual fate of the side-chain theory — and 
certain phases of it carry the aspect of finality — we 
should appreciate as much as possible the extent to 
which it has shaped modern thought, and recognize 



PREFACE. v 

that it has won an imperishable place in the his- 
tory of biologic progress. 

It should also be understood that the utilization 
of the side-chain theory in no sense carries with it 
a negation of the importance of phagocytosis, a 
fact which is plainly set forth on pages 212-215. 
Without doubt the role of the phagocytes in recov- 
ery from a large group of infections is on a better 
and truer basis than it has ever been before, and 
for this condition the recent work on opsonins has 
been most significant. 

In relation to the grouping of the infectious 
diseases adopted in Part Two, attention is called 
to the explanatory paragraph on page 235. 

It will be noted that a complete bibliography of 
the subject of immunity has not been added, and 
this needs no explanation to one who is conscious 
of the massive proportions of the literature. A 
critical analysis of the entire literature, which 
would not have been in harmony with the endeavor 
to present the topics briefly and clearly, and which 
would have made detailed references essential, has 
not been attempted. The works cited in the bibli- 
ography are largely analytic in character and carry 
with them more or less complete references, 
through which those who are so interested may 
reach the original sources easily. This is true par- 
ticularly of the handbook of Kolle and Wasser- 



vi PREFACE. 

mann and of the volume by Metchnikoff. Almost 
the entire fourth volume of the former is devoted 
to the subject of immunity, the enormous litera- 
ture of which is analyzed by different persons of 
international repute. The most recent literature 
on the various subjects is accessible through the 
Index Medicus, or the index prepared semi-an- 
nually by The Journal of the American Medical 
Association. 

The index at the close of this volume serves as 
a glossary of terms, the explanations of which may 
be found on the pages referred to. 

H. T. Eicketts. 

Chicago, February, 1906. 



CONTENTS. 
PART ONE— GENERAL. 

Chapter I. 
Parasitism, Infectiousness. Contagiousness 1- 6 

Chapter II. 
Infectious Etiology 7- 1G 

Chapter III. 
General Considerations 17-23 

Chapter IV. 
History and Development 24- 34 

Chapter V. 
Natural Immunity : 

A. Protection Afforded by the Body Surfaces 35- 41 

B. The Protective Xature of Inflammation. . 41- 46 

C. The Antibacterial and Antitoxic Xature 

of Xatural Immunity 46- 55 

Chapter VI. 
Acquired Immunity 56- 64 

Chapter VII. 

Toxins and Antitoxins 65- 77 

Chapter VIII. 

The "Structure" of Toxins and Antitoxins and 

the Xature of the Toxin-Antitoxin Reaction. . . 78- 91 

Chapter IX. 
The Phenomena of Agglutination 92-104 

Chapter X. 
The Xature of the Substances Concerned in 
Agglutination 105-118 



viii CONTENTS. 

Chapter XI. 

Precipitins 119-129 

Chapter XII. 

A. General Properties of Bactericidal Serum-. .. 130-141 

B. Amboceptors and Complements 141-101 

Chapter XIII. 
Cytotoxins ." 162-175 

Chapter XIV. 
Phagocytosis 176-194 

Chapter XV. 
The Side-Chain Theory of Ehrlich and Its Rela- 
tion to the Theory of Phagocytosis 195-217 

Chapter XVI. 
Principles of Serum Therapy 218-234 

PART TWO-SPECIAL. 

Group I. — Acquired Immunity Is Chiefly Antitoxic. 

A. — Bacterial Diseases: 

Diphtheria 235-244 

Tetanus 244-256 

Botulism 256-259 

Bacillus Pyocyaneus 259-262 

Otner Soluble Bacterial Toxins 262 

B. — Intoxication by Soluble Plant Toxins: 

Hay Fever 262-264 

Other Plant Toxins 264 

C. — Intoxication by Soluble Animal Toxins: 

Poisoning by Snake Bites 264-268 

Other Zootoxins 268 

, Group II. — Acquired Immunity Is Chiefly Anti- 
bacterial. 

Typhoid Fever 269-284 

Paratyphoid Fever 284-288 

Acute Epidemic Dysentery 288-294 



COXTEXTS. ix 

Meat Poisoning by Bacillus Enteritidis 294-298 

Bacillus Coli Communis 298-304 

Cholera 304-315 

Plague 315-327 

Anthrax 327-333 

Malta Fever 333-335 

Group III. — Acute Ixfectioxs ix Which Lastixg 
Immunity Is Xot Established. 

Pneumococcus Infections — Pneumonia 336-349 

Streptococci 349-370 

Staphylococci 370-383 

Micrococcus Catarrhalis 383-384 

Gonorrhea and Other Infections with the Gono- 

coccus 384-388 

Epidemic Cerebrospinal Meningitis 388-393 

Influenza 393-399 

Soft Chancre 399-401 

Bacillus of Friedlander and Other Members of 

the Capsule-Forming Group 401-402 

Relapsing Fever 403-406 

Group IV. — Chronic Ixfectioxs ix Which Lastixg 
Immunity Is Xot Established. 

Tuberculosis 407-445 

Leprosy 445-452 

Glanders 452-458 

Rhinoscleroma 458 

Actinomycosis 458-462 

Madura Foot 462 

Infections by Streptothrix, Cladothrix and Lepto- 

thrix 463 

Oidiomycosis 463-467 

Group V. — Diseases of ProtozoOx Etiology. 

Malaria 468-483 

Trypanosomiasis 483-497 

•Spotted Fever"" of the Rocky Mountain Stales. .497-498 
Texas Fever as an Example of Pyroplasmosi *. . .499-500 
Amebic Dysentery 500-504 



x CONTENTS. 

Sarcosporidia 504 

Balantidium Coli 505 

Cercoinonas Intestinalis 50G 

Trichomonas 507 

Coccidiosis 508 

Group VI. — Diseases of Doubtful or Unknown 
Etiology. 

Hydrophobia 510-521 

Syphilis 522-529 

Yellow Fever 529-538 

Typhus Fever 538 

Dengue Fever 539-541 

Acute Articular Rheumatism 541 

Smallpox and Vaccinia 541-555 

Chickenpox (Varicella) 555 

Scarlet Fever 556-559 

Measles 559-562 

German Measles (Kotheln) 502 

Whooping Cough ' 562-56G 

Mumps 566 



Appendix 567-57 1 

Bibliography 572 

Index 573-599 

Corrections 600 



PART ONE— GENERAL 



CHAPTEE I. 



PARASITISM, INFECTIOUSNESS, CONTAGIOUSNESS. 

Parasitism is the condition in which a plant, or Parasitism. 
an animal being, lives on or within another living 
organism. A true parasite always derives its sus- 
tenance from the tissues of its host. 

Some parasites may live on a host without 
causing appreciable damage, that is, they are non- 
pathogenic parasites. In this case they may de- 
rive their nutrition from some of the excreted non- 
living products of the host, living as pure sapro- 
phytes. 1 or the amount of nutritious substance 
which they obtain from the host may be so little 
that the health of the latter is not impaired. 

There is another large class of parasites, how- 
ever, which under proper conditions cause severe 
diseases in the host. Many pathogenic microbes live 
in and on the skin without doing harm, but if cer- 
tain ones reach the deeper tissues, they may insti- 
tute pathologic processes (e. g., staphylococci). Any 
organism which is able to cause pathologic tissue 
changes or to set up abnormal symptoms is classed 
as a pathogenic parasite. The abnormal processes 
which they set up are our infectious diseases. 



1. A saprophyte is defined as a vegetable organism 
which lives on dead organic matter. An organism which is 
habitually saprophytic may become pathogenic under the 
proper conditions (bacillus of malignant edema). And. on 
the other hand, a pathogenic parasite lives a saprophytic 
life, when it grows in our artificial culture media. 



INFECTION AND IMMUNITY. 



Infectious 
Disease. 



Infestation 
and Infec- 
tion. 



Contagiousness 
and Infectious- 
ness. 



An infectious disease is one which is caused by 
living organisms which in some way have been 
introduced into the tissues of the body. Accord- 
ingly the word has reference to the nature of the 
cause of the disease. It is from the Latin inficire, 
meaning to place in or into. 

Where living organisms exist on a body sur- 
face, as the skin or intestinal tract, the surface is 
said to be infested; the skin, for example, is in- 
fested with pediculi. One may also say that the 
intestinal tract is infested with tape worms, but 
here the distinction between infestation and in- 
fection is not. to be drawn so sharply; surely when 
the larvae penetrate the intestinal wall and reach 
the circulation or distant organs we must speak 
of infection. But even the adult tenia as it ex- 
ists in the intestines may cause erosions of the 
mucous membrane or may perhaps burrow a slight 
distance into the wall, a condition which approx- 
imates the action of the larvae in passing through 
the wall; accordingly at some point the distinc- 
tion between infestation and infection becomes an 
arbitrary one. 

Confusion sometimes arises in using the words 
infectious and contagious. A contagious disease 
is one which may be transmitted from one indi- 
vidual to another by direct or indirect contact; 
the word has reference to the manner of transmis- 
sion of an infection. Xon-infectious diseases are 
never contagious. Contagiousness is well illus- 
trated in those disease in which the transmission 
takes place through the air. as seems to be the 
case in smallpox and scarlet fever. Here there 
may be a contagious zone of atmosphere surround- 
ing the patient, in which the virus is present, and 



coy TACT iyFECTIOy. 3 

by which the agent reaches the lungs of one within 
the zone. Contagiousness is even more striking 
when it takes place through the medium of some 
inanimate substance, such as clothing or toys, 
which were previously within the contagious zone 
or in direct contact with the patient. Such sub- 
stances, fomites, were formerly thought to be of 
great importance in the extension of yellow fever ; 
a theory which has been entirely exploded by the 
proof that the disease is transmitted through the 
bite? of infected mosquitoes. 

Typhoid fever is not highly contagious. There P ^^ 
probably is no infected zone of atmosphere about 
the patient in the sense that there is about a scar- 
let fever patient. Yet it frequently happens that 
the nurse contracts the disease while caring for 
her patient. It is likely that she has in some way 
transferred the bacteria from the patient's sputum, 
urine, feces or skin to her lips or hands so that 
eventually they found their way into the intes- 
tines. At the same time it is not improbable that 
the point of entrance for the germs, i. e., the in- 
fection atrium, may at times be the lungs, the Jj^j 8 " 
bacteria having been inhaled. However, typhoid 
fever is usually a "water borne" disease, seldom 
"air borne." 

We are to look on malaria as a strictly non-con- 
tagious disease, although no doubt is possible as 
to its infectiousness. No amount of personal con- 
tact with the patient will transmit it to another. 
To accomplish transmission the parasite must be 
actually injected into an individual, an event 
which happens exclusively, it is believed, through 
the bite of a mosquito which has previously fed on 
the blood of a malarial patient. 



IXFECTIOX AXD IMlllXITY. 



Tetanus is another noted example of an infec- 
tious disease which is not acquired by contact with 
one suffering from it. 
Pathogenesis. The various parasites have different ways of in- 
juring the body. The itch mite burrows into and 
beneath the epidermis, causing mechanical irrita- 
tion as well as the inflammatory reaction produced 
by its toxic excretions. The loss of blood caused 
by some intestinal parasites, and the hemorrhage 
which follows from the wounds, often lead to 
grave anemias and the general changes which are 
caused by such anemias. This is especially the case 
in the duodenal infection with uncinaria duoden- 
alis (uncinariasis). 

A certain variety of Filaria sanguinis hominis 
produces disorders by mechanically blocking the 
lymph channels. 

The plasmodium of malaria causes anemia by 
the destruction of blood cells. 

The febril disturbances of infectious diseases 
are certainly due to toxic influences. 

It is generally said that bacteria produce dis- 
turbances in both a mechanical and a toxic way. 
However, the more we learn about bacterial infec- 
tions the more important do the toxic pheno- 
mena become. It is doubtful if any pathogenic 
bacterium is entirely devoid of toxic powers. 

It is probable that the bacterial emboli which 
are sometimes found in capillaries and small ar- 
teries cause disturbances through the shutting off 
of so much circulation, but still greater damage 
may result from the action of toxins which are 
formed by the microbes making up the emboli. 

In lobar pneumonia we have a good example of 
a mechanical disturbance of importance. The 



Mechanical 

and Toxic 

Injuries. 



EFFECTS OF TOXIXS. 5 

alveoli become filled with a fibrinous and purulent 
exudate which makes a large area of pulmonary, 
tissue unavailable for respiration. Yet, even here, 
the mechanical disturbance has arisen only as a 
result of the previous toxic action of the pneumo- 
cocci on the capillary walls and the alveolar epithe- 
lium, permitting the escape of the blood and serum. 

The toxins of bacteria often show a remarkable Effects of 
selective action on one organ or another. Some 
destroy the red blood cells to a great degree 
(staphylococcus and streptococcus) ; other toxins 
have a special affinity for the nervous tissue (tet- 
anus) ; some attack particularly the endothelium 
of the vessels, causing many minute hemorrhages. 
Frequently bacterial toxins cause areas of necrosis 
in the lymphoid and parenchymatous organs, and 
the granular degenerations of the latter, in. acute 
infectious diseases, are well known. The albumin 
and casts which appear in the urine in many acute 
febrile diseases are the result of toxic action on 
the epithelium and endothelium of the kidneys. 
It is said that in anthrax all the glycogen may 
disappear from the liver; toxins may disturb the 
functions of various organs to similar degree. 

Some chronic infections are characterized by the 
development of new connective tissue and vessels; 
this is seen especially in tuberculosis, syphilis and 
actinomycosis. The import of the new connective 
tissue depends on its location. A large amount of 
it may form in pre-existing connective tissues with 
no consequent harm ; but even a small scar, gumma 
or tubercle in the brain may cause serious results. 

It has been stated above that infectious diseases infectious 
are caused by living pathogenic organisms. In- Substances - 
vc-tigations have shown, however, that the toxic 



6 INFECTION AND IMMUNITY. 

products of some organisms can be prepared and 
separated from the organisms themselves by filtra- 
tion, and that such microbe-free toxins when in- 
jected into animals may cause the same symptoms 
that are produced by the bacteria themselves (teta- 
nus and diphtheria). Accordingly, for the sake of 
convenience, these toxins also may be considered 
among the infectious agents, even though sepa- 
rated from their corresponding bacteria. The va- 
rious infectious agents, including these toxins, find 
their proper places in the following classification, 
which, for the most part, is that of von Behring : 
I. Living (i. e., pathogenic parasites). 

A. Macroparasites (e. g., intestinal worms, 

pediculi). 

B. Microparasites. 

1. Bacteria (fission fungi: each cell 
divides into two in proliferating) . 

2. Fungi of more complex organiza- 
tion (e. g., aspergillum, oidia). 

3. Protozoa (e. g., plasmodium mala- 
rice, ameba coli). 

II. Non-living (i. e., toxins). 

A. Animal toxins (e. g., snake venom). 

B. Vegetable toxins. 

1. Non-bacterial (e. g., abrin, from the 
jequirity bean; ricin, from the cas- 
tor oil bean; these are strong red 
corpuscle poisons, chiefly of experi- 
mental interest). 

2. Bacterial. 

a. Soluble bacterial toxins (diph- 
theria and tetanus). 

b. Intracellular bacterial toxins, 
which are not secreted by the 
cells in a soluble form. 



CHAPTER II. 



INFECTIOUS ETIOLOGY. 

The microbic cause of a disease must be in hand 
before a logical attempt can be made to prepare a 
specific immune serum. It is not in all cases nec- 
essar}- that the organism be cultivated artificially, 
however ; the conditions in rinderpest may be cited 
in which the body fluids of a diseased animal, 
known to contain the infectious agent, are used 
for immunization, although the microbe itself can 
not as yet be cultivated or recognized. 

There are so many possibilities of error, and so Koch's 
many errors have actually been made in regard to 
infectious etiology, that certain requirements in 
the way of proof are now habitually demanded be- 
fore a particular organism can be accepted as the 
cause of a disease. These requirements are most 
frequently expressed in the form of Koch's laws, 
which may be stated as follows 1. The suspected 
organism must be found constantly in the proper 
tissues of an animal suffering from the disease, or 
which has died from it. 2. The organism must be 
cultivated artificially in a pure state. 3. It must 
be possible to reproduce the disease in a suitable 
animal by inoculation with the pure culture. 4. 
The organism must again be cultivated in a pure 
state from the tissues of the experiment animal. 

Since these laws were formulated another proce- Agglutination 
dure has been developed which may give valuable 
•evidence as to etiology. This pertains to the ag- 
glutination test, or, as we speak of it in connection 
with typhoid fever, the Grnber-YVidal reaction. 



8 INFECTION AND IMMUNITY. 

This principle, that in the acquiring of immunity 
to a microbic infection the serum of an individual 
gains in agglutinating power for the micro-organ- 
ism, has been found to hold true in many infec- 
tions. Consequently, if one has in hand the speci- 
fic micro-organism for a disease, he would expect 
the serum of a patient sick of this disease to have a 
stronger agglutinating power for this micro-or- 
ganism than for others which were accidentally 
present; and this power would also be greater than 
that possessed by the serum of one who had not 
had this particular disease. In spite of some pos- 
- , sibilities of error the agglutination test has been 
of distinct value in the recognition of the specific 
micro-organisms in certain diseases, as in the case 
of the germ of epidemic dysentery (Shiga). 
Obstacles All Koch's laws have not been complied with in 

to Koch s x 

Laws, certain cases, because of various difficulties 
which have been encountered. First, the patho- 
genic protozoa can not be cultivated on artificial 
media (we must except the success of Xovy and 
McNeal with certain tiwpanosomas, and of Strong 
with the ameba coli under symbiotic conditions) : 
second, certain bacteria which may be found con- 
stantly in a given disease have not been cultivated 
artificially (spirillum of recurrent fever) ; third, 
there are a few diseases which are peculiar to man 
and accordingly can not be reproduced in experi- 
ment animals (leprosy, influenza, scarlet fever, 
measles, etc.) ; fourth, some infectious agents are 
pathogenic for experiment animals, but do not 
reproduce in them a clinical or anatomic condition 
identical with that found in the original animal 
(typhoid). 
Furthermore, failure to comply with all the re- 



KOCH'S LAWS. 9 

quirements enumerated does not, in some eases, 
disqualify the organism as the causal factor. If 
an organism is found constantly in characteristic 
sites in a given disease and not in other infections, 
and if at the same time other microbes are not 
present or are present inconstantly or through ac- 
cident, there could be little or no hesitation in ac- 
cepting this organism as the cause of the disease, 
even if it were impossible to cultivate it or to trans- 
fer the disease to animals. The typhoid bacillus 
has been cultivated from characteristic foci (stools, 
blood, spleen, urine, rose spots) in such a large 
number of cases, and the bactericidal and agglu- 
tinating powers of the patient's serum against this 
organism are so distinctive, that compliance with 
the third law, though desirable, is not now essen- 
tial. The conditions are similar in reference to 
cholera and the cholera vibrio. 

The conditions are so unique in some diseases 
that, although all Koch's laws have not been met 
literally, certain equivalents have been met. To 
illustrate, we may consider an anopheles mosquito 
which has become infected with the plasmodium 
of malaria by biting a malarial patient, as a cul- 
ture medium ; and the transferring of the infection 
to another patient by the bite of this mosquito as 
the inoculation experiment which is desired. 

The term "specific infectious disease" has come Specific 
to have a very special meaning. It is applied to a Diseases. 8 
disease having characteristic clinical and anatomic 
phenomena, which can be caused only by one par- 
ticular micro-organism. Among the disease? 
which come within the limits of this brief defini- 
tion, the following may be enumerated (the micro- 
organism which is the cause of each disease being 
also given) : 



10 



INFECT I OX AND IMMUNITY. 



(Unknown 
Etiology. 



Diphtheria 

Tetanus 

Typhoid fever 

Cholera 

Anthrax 

Tuberculosis 

Leprosy 

Plague 

Dysentery 

Influenza 

Glanders (farcy) 

Chancroid 



Bacillus diphtherice 

Bacillus tetani 
Bacillus typhosus 
Vibrio cholera? 
Bacillus anthracis 
Bacillus tuberculosis 
Bacillus lepra 
Bacillus pestis 
(bacillary) Bacillus dysenteries, 
Bacillus influenzas 
Bacillus mallei 
Bacillus chancri mollis 

(Ducrey) 
Spirillum obermeieri 
Micrococcus gonorrliece 
Diplococcus intracellula- 
ris meningitidis (of 
Weichselbaum) 
Actinomyces bovis et 
ho minis 
Blastomycosis Blastomycetes and Oidia 

Malaria Plasmodium malaria? 

A large number of animarHiseases have their 
specific microbes, as do certain other human dis- 
eases which hardly concern us as to the subject in 
hand. 

In addition to the diseases mentioned, there are 
several, of unknown etiology, which from analogy 
we must recognize as specific. Scarlet fever, 
measles, German measles, chickenpox, smallpox, 
yellow fever, typhus fever, hydrophobia and syphi- 
lis, are undoubtedly due to micro-organisms. Mal- 
lory recently found in the skin of four scarlet 



Recurrent fever 
Gonorrhea 

Epidemic cerebrospi 
nal meningitis 

Actinomycosis 



UNKNOWN ETIOLOGY. 11 

fever patients a protozoon-like body which he be- 
lieves to be the cause of the disease, although he 
admits that much desired proof has not been ob- 
tained. The Diplococcus scarlatince of Class, 
which a few years ago acquired some notoriety, 
has not been able to stand as the cause of scarlet 
fever in the face of rigid investigation. 

Parker, Beyer and Pothier have announced the 
discovery of a protozoon (?) Myxococcidium 
stegomyicBj in the mosquitoes which infect man 
with yellow fever ; but Carroll maintains that this 
organism has no relation to the production of the 
disease. The Bacillus icteroides, which Sanarelli 
found in a rather high percentage of cases, is now 
generally considered as a contaminating organism. 

It is possible that smallpox and vaccinia will be 
eliminated from the diseases of unknown causa- 
tion, owing to the evidence of protozoon etiology 
that Councilman and his colaborers have obtained ; 
however, for the present, the question may be con- 
sidered sub judice in view of the fact that the 
forms described bear a close resemblance to cer- 
tain well-known types of cell degeneration. 

The following animal diseases, of unknown 
etiology, may also be mentioned in this connec- 
tion: Foot and mouth disease, peripneumonia, 
bovine pest, sheep-pox (clavelee), chicken-typhus 
or chicken-pest and epithelioma contagiosum of 
fowls. 

The following appear to be the chief reasons for obstacles to 

Discovorv of 

the failure to discover the organisms of these dis- Microbes. 
eases: 1. Inability to cultivate the microbe. 2. 
Mixed, or symbiotic infections. It is conceivable 
that in some case the combined action of two 
micro-organisms may be necessary to cause the 



INFECTION AND IMMUNITY. 



Filterability 
•of Viruses. 



Non-Specific 
Infectious 
Processes. 



disease. The non-toxic products of the two may 
synthesize to form a toxic substance (Hektoen.) 3. 
Unstained ability of the microbe. 4. Ultramiscro- 
scopic size. The organism of the peripneumonia of 
cattle was cultivated by Nocard and Eoux by grow- 
ing it in a closed collodion sac which was placed in 
the peritoneal cavity of suitable animals. It is so 
small that its form can not be made out, and 
growth is recognized onty by clouding of the 
culture medium, and the increased virulence of the 
latter for animals. 

Some valuable information has been obtained 
by observing whether the infectious agents arc 
so small that they will pass through dense niters 
of porcelain or infusorial earth. It has been found 
that the viruses of foot and mouth disease, peri- 
pneumonia, rinderpest, sheep-pox, chicken-typhus, 
horse sickness, epithelioma contagiosum of fowls, 
and yellow fever are filterable, i. e., they pass 
through the filter. This is determined by inject- 
ing the filtered culture medium or serum into sus- 
ceptible animals. The viruses of smallpox and 
vaccinia are said to be non-filterable. Success in 
filtering the hydrophobia virus has recently been 
claimed by Eemlinger. Inasmuch as scarlet fever, 
measles, chicken-pox, typhus fever and syphilis* 
can not be produced in animals, the filterability of 
their viruses is not at present susceptible of dem- 
onstration. 

There is a marked tendency in many diseases, 
typhoid, cholera, malaria, etc., for characteristic 
organs or groups of organs to be involved in some 
particular manner. These are features which 



* Recently syphilis h;is been inoculated successfully 
into anthropoid apes. (Metchnikoff and Roux.) 



XOX-SUSCEPTIBILITY. 13 

stamp them as specific diseases. On the other 
hand, a large number of micro-organisms cause no 
well-defined clinical and anatomic disease, but, 
depending on various accidents, cause an inflam- 
mation now in one organ, now in another. 

Suppuration is not a specific disease, because 
the pyogenic power is common to a large number 
of microbes. A diphtheritic or pseudo-diphtheri- 
tic process in the mouth and throat may be caused 
by the diphtheria bacillus, streptococcus, staphylo- 
coccus, oidium or yeasts ; bronchitis may be caused 
by the influenza, tubercle, plague and typhoid 
bacilli, and by the infecting agents of the acute 
exanthemata, etc. ; pulmonitis by the pneumococ- 
cus, streptococcus, tubercle, plague, Friedlander 
and influenza bacilli, oidium, actinomyces, etc. ; 
meningitis by the tubercle and influenza bacilli, 
streptococcus, staphylococcus, pneumococcus, gono- 
coccus, diplococcus of epidemic meningitis, the 
syphilis virus, etc. ; arthritis by the streptococcus, 
staphylococcus, tubercle bacillus, gonococcus, the 
virus of rheumatic fever, etc. ; endocarditis by the 
streptococcus, staphylococcus, gonococcus, pneu- 
mococcus, tubercle bacillus, etc.. and septicemia 
by a whole host of organisms aside from those 
mentioned as causing specific diseases. 

Within certain limits, however, there is often a 
degree of specificity in the processes produced by 
some of the organisms mentioned, which some- 
times allows of clinical and anatomic differentia- 
tion. The infiltrating and rapidly extending in- 
vasion of the subcutaneous and connective tissues 
caused by the streptococcus can often be distin- 
guished clinically from the slower, more circum- 
scribed process of the staphylococcus. The condi- 



Infections. 



14 INFECTION AND IMMUNITY. 

tions induced by the Bacillus aerogenes capsulatus, 
the bacillus of malignant edema, are, in turn, dif- 
ferent from those of the streptococcus and staphy- 
lococcus. The pneumococcus commonly causes 
the consolidation of rather extensive areas of the 
lung, whereas the streptococcus and the bacillus 
of Friedlander are more often found in the lobu- 
lar consolidations. The membranous inflamma- 
tion of diphtheria may in favorable cases be distin- 
guished from that of the pyogenic organisms with- 
out bacteriologic aids ; in this possibility, however, 
there lies no justification for neglect of the bac- 
teriologic examination. 
Mixed The coexistence of two or more micro-organisms 
in a morbid condition is of frequent occurrence, 
and some of the most interesting and important 
phenomena of infectious diseases are referable to 
mixed, secondary or superimposed infections. 

Two exogenous infections may attack an indi- 
vidual at the same time. Measles and scarlet fever 
and diphtheria and scarlet fever have been known 
to coexist. Pneumococcus pneumonia and typhoid 
fever, chancre and soft chancre with pus cocci, 
syphilis and gonorrhea, diphtheria with strepto- 
cocci, tetanus with gangrene-producing organisms, 
are common observations. One organism may in- 
tensify the virulence of another. Diphtheria ac- 
companied by streptococcus infection seems to be 
more virulent than diphtheria alone. It is also 
believed that the presence of aerobic organisms 
(those which demand oxygen for their develop- 
ment) in a wound infected with the tetanus bacil- 
lus or the bacillus of malignant edema (anaerobic 
organisms), may increase the virulence of these 
infections. Streptococci are probably important 



MIXED INFECTIONS. 15 

organisms in scarlet fever, for they are present in 
unusual numbers in the throat lesions and are 
often found in fatal cases in all the organs, yet it 
is believed that they constitute only a mixed or 
secondary infection superimposed on that of the 
scarlatina virus. The conditions are somewhat 
similar in smallpox, the pustules of which invari- 
ably contain streptococci, staphylococci, or both. 
In both scarlatina and smallpox these secondary 
infections may be responsible for many fatalities. 

Pneumococcal s pneumonia occurring during the 
course of, or during convalescence from the erup- 
tive fevers, diphtheria, typhoid fever or erysipelas ; - 
a streptococcus septicemia developing during 
typhoid (giving rise to an irregular temperature 
curve), streptococcus infection of tubercular cavi- 
ties, and the development of acute tuberculosis 
during measles — these are important examples of 
secondary infections. 

We should naturally expect that the presence of 
a severe secondary infection might embarrass at- 
tempts at serum therapy. Experience on this 
point is practically limited to diphtheria, and 
there is no lack of evidence to show that the dis- 
ease when complicated by severe streptococcus in- 
fection often can not be controlled by antitoxin 
treatment. 

It may be emphasized that there are certain dis- infectious 
eases in which a wide dissemination of the bac- 
teria is not necessary for the production of morbid 
phenomena; where, in fact, they may be entirely 
localized (diphtheria, tetanus), and the symptoms 
are produced by virulent toxins which are readily 
dissolved in the body fluids and carried to impor- 
tant organs. More especially are those microbes 



10 INFECTION AND IMMUNITY. 

placed in this class which produce their specific 
disease-producing toxins in a soluble form when 
grown in our artificial culture media (bouillon). 
The bacilli of diphtheria, tetanus, botulism and 
the pyocyaneus bacillus belong distinctively to this 
group. 

Snake venom and arachnolysin (spider poison) 
are the best known examples of soluble animal 
toxins. As will appear later, the serums of all 
animals probably contain a variety of toxins which 
are injurious to one or more species of animals. 






CHAPTEE III. 



GENERAL CONSIDERATIONS. 

By immunity we understand that condition in Definition. 

which an individual or a species of animals exhib- 
its unusual or complete resistance to an infection 
for which other individuals or other species show 
a greater or less degree of susceptibility. Immune 
is from the Latin immunis, which originally ap- 
plied to one who was exempt from a public service, 
exempt from tribute, or free. Although the word 
retained this civil meaning for centuries, and still 
retains it in certain connections, it also had, even 
in ancient times, a limited application to the pro- 
tection which an individual might possess against 
poisons. It is seen, for example, in descriptions 
of a tribe inhabiting Northern Africa, the Psylli, 
who possessed a natural immunity to the bites of 
poisonous snakes. Although we may be certain 
from this and other references that a condition of 
immunity was recognized in very ancient times, 
the present significance of the term has developed 
largely from a better understanding of the nature 
of infectious diseases and of the conditions upon 
which the resistance of the body depends. 

As the definition suggests, we do not think of Diseases 
immunity to such processes as Bright's disease, immunity. 
arteriosclerosis or the metabolic diseases, but only 
to those which we have learned to recognize as in- 
fectious. 

Immunity has no necessary relationship to the 
degree of contagiousness of an infectious disease, 



IS 



INFECTION AND IMMUNITY. 



Acquired 
Immunity. 



Natural 
Immunity. 



Family Suscep- 
tibility and 
Immunity. 



although some of the most striking and certainly 
the most common examples of immunity are seen 
in relation to such infections (as scarlet fever and 
smallpox). Tetanus, on the other hand, which is 
absolutely non-contagious, can likewise give rise 
to a high degree of immunity. 

JSTo medical fact is more widely known among 
intelligent people than that an attack of certain 
of our infectious diseases brings about some kind 
of change in the patient's tissues which protects 
him, or renders him immune, against further at- 
tacks of the same disease. Inasmuch as he was 
previously susceptible, the new property is an ac- 
quired one, and he is now said to possess an ac- 
quired immunity against this infection. 

It is also well known that many diseases which 
attack man can not be inoculated into animals, 
and biologists are familiar with many examples 
of immunity which are confined to particular spe- 
cies. The lower animals apparently can not be in- 
fected with scarlet fever or measles, nor man with 
chicken cholera. The negro is less susceptible 
than the white man to yellow fever. The resist- 
ance which these examples illustrate has occurred 
naturally, not through having the disease; it is a 
natural immunity. 

Natural immunity is, for the most part, an in- 
herited condition; this certainly is the case where 
a whole class of animals is involved. Similarly, 
the susceptibility which is peculiar to a species 
must be hereditary. It is often said of some dis- 
eases that they run in families; e. g., carcinoma, 
gout, insanity. This appears to be just as true of 
some infectious diseases, the most noteworthy ex- 
ample of which is probably tuberculosis. In con- 



NATURAL IMMUNITY. 19 

trast to this inherited susceptibility is an inherited 
immunity, which may also run in families. It is 
not so easy to adduce examples of this. We are in 
the habit of thinking of the individual who can 
resist all infections as representing a standard. 
He, however, is above the average in resistance, 
and the average is our proper standard for esti- 
mating the resistance of a species or race of ani- 
mals. It is undoubtedly true that some families 
possess an unusual resistance to tuberculosis. 
Furthermore, experimental work with animals has 
proved that, within limits, an immunity to cer- 
tain infections (e. g., tetanus) acquired by a fe- 
male may be transmitted to her offspring. Even 
in a given family, however, there are often marked 
variations in susceptibility and resistance. One 
child may contract scarlet fever, while his brother, 
living under exactly the same conditions, may 
escape it. There is, moreover, much reason to be- 
lieve that the same individual varies greatly in his 
resistance at different times and under different 
conditions. Hence, the personal equation, as rep- 
resented by individual resistance or individual sus- 
ceptibility, is of no small consequence. 

The facts mentioned were familiar long before 
anything was known regarding the principles on 
which they depend. Subsequent to the discovery 
of some of these principles (to be considered 
later), it became convenient and necessary to rec- 
ognize other special types of immunity, although 
any type which can be conceived must still find a 
place under either natural or acquired immunity. 

Although such diseases as typhoid and cholera Antibacterial 

. -, , n . • , and Antitoxic 

are accompanied by pronounced toxic symptoms, immunity. 
the poisonous substances seem to be integrally as- 



20 INFECTION AND IMMUNITY. 

sociated with the bacterial protoplasm and not 
secreted in a soluble or diffusible form by the liv- 
ing cell; they are spoken of as intracellular toxins 
or endotoxins. Observations point to the belief 
that the endotoxins are liberated only after the 
bacteria are killed and dissolved. When one, 
through infection, has acquired immunity to ty- 
phoid or cholera, his fresh serum is able to kill the 
respective bacterium, but apparently is not able to 
neutralize its toxic substance. Hence, on the basis 
of the nature of the serum, immunity to such dis- 
eases is spoken of as antibacterial rather than 
antitoxic. On the other hand, the symptoms which 
are so characteristic of tetanus are produced not 
by contact of the bacteria with the nervous system, 
but rather through the specific soluble toxin which 
is secreted by the bacilli in the wound where they 
reside. This poison, or toxin, is .carried from the 
wound to the nervous system through the lymph- 
atic or blood circulation, the bacterium itself not 
being transported. Therefore, although tetanus is 
a bacterial disease, it is at the same time and in a 
peculiar sense a toxic disease. 

The serum of an animal which has acquired im- 
munity to diphtheria or tetanus neutralizes the cor- 
responding soluble toxin, but does not necessarily 
injure the micro-organism itself. That is to say. 
the immunity is antitoxic. Experience has shown 
that this distinction between antibacterial and an- 
titoxic immunity is an important one, and the 
differentiation is very sharp in some instances. 
In many examples of natural immunity, the re- 
sistance can not be attributed so specifically to anti- 
bacterial or antitoxic serum properties. This is re- 
ferred to later. 



ACQUIRED III MUX ITT 



21 



Immunity which, results from an infection de- ^nufnity 
pends on a specific reaction on the part of the 
tissue cells in response to the chemical injury pro- 
duced by the bacteria or their toxins. The indica- 
tion of the occurrence of such a reaction lies, first, 
in the recovery of the patient, and, second, in the 
new antitoxic or antibacterial power which may be 
demonstrated in the serum. In view of the active 
part played by the body in establishing this new 
resistance, the condition is referred to as an active 
immunity. In the preparation of various anti- 
toxic and antibacterial serums for commercial pur- 
poses, a condition of active immunity is deliberate- 
ly produced in the animals (the horse, for exam- 
ple) by the injection of the toxins or of the bac- 
teria. 

Contrariwise, the resistance which is established JjJ 88 '^ 
in an individual through the injection of an im- 
mune serum (such as diphtheria antitoxin) is a 
passive immunity, since it depends on the intro- 
duction of ready-made immunizing substances 
rather than on their production through an active 
process on the part of the one injected. Active 
and passive immunity, then, are varieties of ac- 
quired immunity. Depending on the disease 
which caused the immunity, or on the character 
of the serum injected, they may be either anti- 
bacterial or antitoxic. 

Any one of the types mentioned may be either Relative and 
relative or absolute; synonyms are partial and immunity. 
complete. If absolute, infection is impossible. If 
only relative, different conditions may be made 
to prevail which would render infection possible; 
for example, a large number of bacteria will often 
cause an infection where a smaller number fails 



22 INFECTION AND IMMUNITY. 

to do so. There may also be a temporary decrease 
in one's resistance through overwork, hunger or ex- 
posure. Immunity is usually relative. 

C,aS io i ?T at «r ^ proper combinations of the terms which 
have been enumerated, one may describe somewhat 
accurately the different forms of immunity. Thus, 
a child which has received a prophylactic injec- 
tion of diphtheria antitoxin is in a state of ac- 
quired passive antitoxic immunity to diphtheria. 
If immunity to typhoid has developed as a result 
of the disease, the condition is that of an acquired 
active antibacterial immunity, etc. Accordingly, 
although the terms may be somewhat confusing, 
it is seen that they are in no sense contradictory. 
The following classification of immunity is con- 
venient, although in giving it, we must recognize 
that it probably does not include all types of im- 
munity. At this point the single example may be 
cited, that the chicken is very resistant to tetanus 
toxin, although its serum contains no antitoxin ; 
hence in this instance we could hardly speak of 
antitoxic immunity to tetanus, but rather of non- 
susceptibility to the toxin. 

f Natural. 1 

The inherited immunity of species and Anti- 
varieties of animals. I bacter- 
Inherited family or individual immunity. }- ial or 
Acquired. Anti- 
Active, toxic. 
Passive. J 

, . ^ D . ru 9 In many of these conditions proper biologic ox- 

Habituation. — n i . , n 6 . ,, 

penments will demonstrate the presence of the 
antibacterial or antitoxic substance in the serum 
of the animal which possesses the immunity. The 
technic of such experiments will be illustrated later. 
There is another kind of acquired resistance 
which properly may be mentioned here. It is a 



Immun- 
ity. 



DRUG HABITUATION. 23 

well-known fact that one may gradually accus- 
tom himself to enormous doses of morphin, ar- 
senic, alcohol and some other drugs. A priori, it 
would seem that this condition of resistance 
should be analogous to that which is present in 
antitoxic immunity. But, on the contrary, the 
serum of a morphin or alcohol habitue has no 
power of neutralizing the effects of morphin or 
alcohol. The conditions on which this resistance 
depends are not understood. 



CHAPTEE IV. 



HISTORY AND DEVELOPMENT. 



Early Times and The conception of the nature of immunity 
which was current at one period or another of 
history had some relationship to the conception 
of the etiology of diseases at those times. It will 
be remembered that at one time diseases were 
supposed to be imposed by an angry deity, and to 
avert them various mysticisms were resorted to, 
such as the utterance of incantations and the 
wearing of talismans. On the other hand, a more 
logical attempt to explain the natural immunity 
of the Psylli against snake poison was made by 
Pliny, who suggested that it might be due to their 
habit of drinking water from wells in which pois- 
onous snakes dwelt. This is not unlike our pres- 
ent conception of active immunization. 

Von Behring quotes literature to show that 
among some primitive races of to-day, artificial 
immunization is carried on; a Mozambique tribe 
is said to inoculate against snake poison by rub- 
bing into a small cutaneous incision a paste which 
contains venom. Probably non-fatal quantities 
are introduced in this wa}^ resulting in the forma- 
tion of venom antitoxin, a method comparable to 
that used in the production of diphtheria anti- 
toxin. 

At a very early period the possibility of habitua- 
tion to poisonous drugs was recognized. We learn 
that Mithridates by taking gradually increasing 
doses of poisons established in himself resistance 



EARLY CONCEPTIONS. 25 

of this sort. It is stated also that he fed ducks 
with poisons and then proposed to use their blood 
as an antidote (serumtherapy). The importance 
of antidotes in the minds of the ancients may be 
appreciated from the fact that epidemic diseases, 
such as plague, cholera and smallpox, were at one 
time considered as due to unknown poisons, which 
might be comparable in nature to some known 
poisons, as aconite. Mercury for syphilis, quinin 
for malaria, and salicylic acid for rheumatism 
would certainly have fallen into the category ' of 
antidotes, and mercury may have been so con- 
sidered. 

A historic illustration of the treatment of dis- 
ease on a supposed etiologic basis is found in a 
theory which was prevalent in the seventeenth 
century, according to which diseases were either 
acid or basic in character, and hence should be 
treated, the one with an alkali, the other with an 
acid. Sylvius considered plague to be of acid 
nature and administered alkalies, while Etmuller 
took the opposite view. 

Manifestly, rational treatment and prophylaxis 
of the infectious diseases could not be undertaken 
until their etiology was correctly understood. Yet 
here, as so often happens in medicine, empiricism 
preceded rationalism. For example, protective 
inoculation did not become a principle until the 
time of Pasteur, yet it had been practiced against 
smallpox for centuries, and the method put on 
its present basis by Jenner long before there was 
any idea as to the principles involved in the pro- 
tection. 

The belief that invisible "animalcules" are able Micro- 

i • -, -, , organisms. 

to cause morbid processes in man is a very old 



The 
Microscope. 



26 INFECTION AND IMMUNITY. 

one. A passage from Varro (116-27 B. C.) reads 
as follows: "There are swampy places in which 
grow animals never so small which may not be 
recognized by the naked eye, and which gain ac- 
cess to the body through the air and bring about 
severe diseases." 

The discovery and use of the compound micro- 
scope in the seventeenth century disclosed the 
reality of the minute living forms which had been 
suspected so often. Kircher, with his first crude 
microscope (1646), examined the tissues of va- 
rious diseases, and was the author of many the- 
ories as to their etiology. It is now believed that 
the magnification of Kircher's microscope was so 
small that many of the "worms" which he saw 
were really larger fungus cells and in some in- 
stances the as yet undiscovered blood and pus 
cells. 

Leeuwenhoek (1632-1723), a Dutch naturalist, 
with his compound microscope magnifying 1,000 
diameters, described accurately many microscopic 
forms, but made no application of his discoveries 
to medical problems; nevertheless, such applica- 
tion was not wanting, and the succeeding century 
and a half saw such voluminous descriptions of 
microbes, so many contradictory theories and 
statements concerning their relationship to in- 
fections, that the "infmitesimally small" fell into 
disfavor in many quarters as the cause of diseases. 
The attractions and reasonableness of the theory, 
however, were such that it continued to gain ex- 
ponents, and in the early part of the nineteenth 
century reached a degree of definiteness. In 1855, 
the great French physician, Bretonneau, affirmed 
that a specific germ was the cause of every con- 



MICROBIC SPECIFICITY. 27 

tagious disease: "An epidemic disease can orig- 
inate and extend only through the agency of the 
germ producing it." Yet at this time no infec- 
tion had been definitely proved to be of microbic 
origin. 

In 1850 Eayer and 'Devaine made an observa- Anthrax - 
tion, whicji might have fallen into the oblivion of 
many preceding ones had it not been confirmed by 
later investigators. They found "small filiform 
bodies" in the blood of sheep which had died of 
anthrax, and were naturally inclined to believe 
that these forms caused the disease. Other stu- 
the study of anthrax, with the result that the x* i 
the study of anthrax, with the, result that the y • 
small rods of Devaine were scientifically proved to 
be its cause. 

Two great minds dominated medical research Fermentations. 
at this time — Pasteur and Koch. Pasteur, in his 
early career as a chemist, had had his attention 
called to the processes of fermentation. He re- 
curred to this subject at a time when the theory 
of the spontaneous generation of small living 
forms was widely discussed, and in 1857-1861 
proved beyond any possibility of doubt that lactic 
acid, alcoholic and butyric acid fermentations were 
due to the action of minute living cells ; and, fur- 
thermore, that each particular kind of fermenta- 
tion had its own peculiar microbe as the cause. 
This was an example of what we term to-day 
microbic specificity. Pasteur then applied what Microbic 
he had learned about fermentations to the study Specificity. 
of the diseases of wines and beers. He found their 
causes, and devised a preventive measure, which 
consisted merely in the destruction of the germs 
by heating the wine to a suitable temperature be- 



28 INFECTION AND IMMUNITY. 

fore it was stored. At the instance of the French 
government, he then studied certain diseases of 
silk worms. His success in discovering their 
causes and prevention must always remain for 
us one of the landmarks of the world's progress. 
It was during the latter -investigations that he 
took up the study of anthrax. The specific mi- 
crobe having been discovered, and the methods of 
transmission of the malady having been made 
clear through investigations by both Pasteur and 
Koch, Pasteur turned his attention to methods 
of prevention and, if possible, of cure. 
Vaccination. Pasteur pondered the question of smallpox vac- 
cination. He came to believe that vaccinia was 
smallpox, the virus of which had been attenuated 
by its passage through the cow, and that conse- 
quently when man was vaccinated he was inocu- 
lated with a benign form of the disease. Might 
not this be an example of a law which would be 
general in its application? The protective inocu- 
lation (active immunization) against the pleuro- 
pneumonia of cattle which had long been prac- 
ticed gave encouragement to this hope. Some 
work by Toussaint was important in the answer 
to this question. It was evident that a weakening 
or attenuation of the bacteria or virus must first 
be obtained before it could be safely injected into 
animals for the purpose of producing immunity, 
for if the unaltered virus were injected the viru- 
lent infection would result. Accordingly, Tous- 
saint heated the blood of a sheep which had died 
of anthrax, to a temperature of 55° C. for ten 
minutes, then injected it into a number of sheep. 
Some of the animals died of anthrax, while others 
suffered only a mild attack from which they re- 



Anthrax. 



HYDROPHOBIA. 29 

covered; the latter were found to be immune to 
a subsequent inoculation with virulent blood. In- 
asmuch, however, as some of Tbussaint's animals 
had died of anthrax, Pasteur concluded that there 
was some grave error in technic. He considered 
that Toussaint's method probably killed or atten- 
uated the fully-developed bacilli, but did not in- 
jure the spores of the parasite (Koch had pre- 
viously shown the existence of anthrax spores). 
After much experimentation, Pasteur hit on . the 
plan of growing the bacillus at a temperature of 
42° C, obtaining in this way a culture of the 
fully developed organism which had a low viru- 
lence, but which did not form the dangerous 
spores. When sheep were inoculated with the 
proper amount of this culture, which became 
known as anthrax vaccine, they had a mild attack 
of the disease, which rendered them immune to 
virulent inoculations. 

With the possibility of protective inoculation Hydrophobia. 
with a known virus actually demonstrated, sim- 
ilar procedures were tried with other animal dis- 
eases of known bacterial etiology, with the result 
that successful vaccines against chicken cholera 
and swine plague were developed. Somewhat 
later, having failed in their attempts to discover 
the microbes of plague and cholera, Pasteur and 
his co-workers turned to the study of hydropho- 
bia. All efforts to cultivate the virus from the 
spinal cord of rabid dogs, which surely is its seat 
in the affected animal, failed. The unique idea 
then occurred to consider the infected spinal cord 
as a fully developed culture of the virus. It re- 
mained to subject such a culture to the proper 
attenuating conditions for the purpose of weaken- 



30 INFECTION AND IMMUNITY. 

ing or actually destroying its virulence in order to 
make it fit for protective injections. This was ac- 
complished by drying the cords in a closed vessel 
over a hygroscopic substance (solid potassium 
hydroxid), the final virulence of the cord depend- 
ing on the length of time it had been subjected 
to the drying process. The technic of the protec- 
tive injections, the success of which is household 
knowledge, will be the subject of later considera- 
tion. 
Two important Of primary importance, during this period, was 
the work of Koch on the specific bacteria of tu- 
berculosis, cholera, typhoid and the pyogenic dis- 
eases; and not least his improved methods of ob- 
taining pure cultures through the use of solid 
media (gelatin) on plates. Through his work and 
that of Pasteur two great principles had been 
set in motion ; the microbic specificity of infectious 
diseases, and protective inoculation in its general- 
ized form, through the use of attenuated virus. 
Theories of The scientific mind turned at once to the in- 

theCauseof . 

immunity, quiry, What changes in an animal body are re- 
sponsible for the immunity which is acquired as 
the result of protective inoculations? Also, upon 
what properties of the tissues or body fluids does 
the natural immunity of an animal depend, and 
does the susceptibility of one species depend on 
Exhaustion the absence of those properties which characterize 
the natural immunity of another species? Pas- 
teur had observed that if he grew the microbe of 
chicken cholera in a liquid medium for some time, 
then removed the bacteria by filtration, the fluid 
became unfit for the further growth of the organ- 
ism on subsequent reinoculation. That is, the 
nutrient material had been used up; and he sug- 



PHAGOCYTOSIS. 



31 



gested that this is the case in the body of an ani- 
mal. Having undergone the infection, suitable 
nutrient material for the microbe is used up, and 
recovery ensues. The prolonged absence of the 
proper nutritious substances would account for 
the more or less permanent nature of the acquired 
immunity. This conception, the exhaustion 
theory, at one time shared by Koch and Klebs, is 
still represented in an altered form by Baumgar- 
ten, who speaks of an unfavorable culture medium 
as representing the condition of the immune body, 
which, of course, is broadly true. 

Chauveau was the author of another historic R™ention 
theory of acquired immunity (the noxious reten- Theory. 
tion theory), which maintained that during the 
course of a disease the bacteria produce substances 
in the presence of which they can not develop 
further; consequently recovery takes place, and 
the continued presence of these noxious substances 
renders another attack of the disease impossible. 
Although it is true that bacteria do not grow well 
in their own metabolic products, theories of im- 
munity on this and similar bases are not in ac- 
cord with the fact that immunity may be of great 
duration, and that it may be conferred by the 
injection of the killed bacteria, or, in some cases, 
of their non-living soluble products. 

MetchnikorT may be credited with having first Phagocytosis. 
offered a plausible explanation of natural resist- 
ance, founded on observation. As a zoologist he 
had studied the subject of intracellular digestion 
in the lower animals, and it was while working on 
this problem that he observed the fate of a yeast 
fungus (Monospora), which caused epidemics 
among the daphnia, small, transparent animals 



32 INFECTION AND IMMUNITY. 

with which he was working. Near the alimentary 
tract, which was the infection atrium, some large 
mesoblastic cells, which are perhaps analogous to 
the white blood cells, were seen to ingest the para- 
sites and dissolve them. If this took place to a 
sufficient extent the animals recovered; if, how- 
ever, the infecting organisms were too numerous 
or the reaction on the part of the animal insuffi- 
cient, the body became overwhelmed with para- 
sites and death resulted. Since that time Metch- 
nikoff has evolved his well-known theory of pha- 
goc}rtosis as the essential factor in both natural 
and acquired immunity, a theory which Pasteur, 
in his later years, looked on with favor. We may 
speak of this as the cellular theory of immunity; 
a theory which has had to undergo important 
modications in order to bring it into accord with 
new facts. 
investigation Considering that natural or acquired immunity 
ties of serums, must exist because of certain qualities of the body 
cells, or of the body fluids, or possibly of both, 
investigators began to make analyses of the tis- 
sues; and of all the analyses, that which we may 
term the biologic has been the most fruitful. In 
this case biologic analysis means the detection of 
reactions which ma}^ occur when bacteria or their 
products are placed on contact with tissue cells 

Bactericidal or fluids, either in the living animal or in test- 
Power. . . 

glass experiments. The chief of these are the de- 
termination of the ability of the serum of an ani- 
mal to kill bacteria or to neutralize bacterial 
toxins. These important investigations, still in 
their infancy, were inaugurated by the findings 
of Fodor, Nuttall, Nissen, v. Behring and Buch- 
ner, which showed that fresh denbrinated blood, 



PROPERTIES OF SERUMS. 33 

and the blood serum of various animals, were able 
to kill bacteria in the reagent glass. In contrast 
to the action of ordinary antiseptics, this power is 
often selective, killing one variety of bacterium 
and leaving another unharmed. This was of enor- 
mous importance, as it seemed to identify the 
factor on which natural antibacterial immunity 
depends. Then followed the discovery of Mssen 
and v. Behring (Yihrio metchnilcovi) , and of 
Bouchard {B. pyocyanetis) , that if an animal is 
systematically injected, i. e., immunized, with a 
micro-organism, the power of its serum to kill 
the bacterium used in the immunization is greatly 
increased; from which it would seem that acquired 
immunity depends on the increase of powers which 
are normally present to a certain degree. These 
observations have to do with the bactericidal power 
of serum. 

Further progress was made through the discov- Toxins 
cry that the tetanus bacillus (Brieger and Frankel) 
and the diphtheria bacillus (Eoux and Yersin) 
secrete each a powerful, specific, soluble toxin, 
which may be separated from the bacteria by fil- 
tration. Immunization with these bacterium-free 
toxins was undertaken (Behring and Kitasato, 
1890) with the familiar result of the production 
of the specific antitoxins. Other investigations in 
this rli recti on soon showed the independence of 
the antibacterial and the antitoxic properties of 
serums. 

With these facts in hand, the vigor with which 
investigations have been pushed may be readily 
imagined. The hope naturally prevailed that phy- 
sicians might become the masters of all infectious 
diseases, through the possession of specific anti- 



Antitoxins. 



34 INFECTION AND IMMUNITY. 

bacterial and antitoxic serums. But failures, with 
which we are only too familiar, met the attempts 
to produce adequate antiserums for many diseases. 
Nevertheless these failures, through stimulation 
to closer study, have resulted in the accumulation 
of much additional knowledge concerning the 
pathogenic properties of different bacteria, the 
nature of the immune serums and the various pro- 
tective factors of the body. Ehrlich has evolved 
a new theory of immunity from facts which were 
discovered in his laboratory, the " side-chain" 
theory, which it is the purpose to utilize in the 
interpretation of many reactions which will come 
up for consideration. 



CHAPTER V 



NATURAL IMMUNITY. 
A. PROTECTION AFFORDED BY THE BODY SURFACES. 

Virulent organisms (e. g., staphylococci and The 
streptococci) exist normally on the skin or be- 
tween the superficial horny cells, some exceptional 
circumstance being necessary, e. g., wounds, to en- 
able them to penetrate deeper and to cause disease. 
It is evident, then, that the physiologic shedding 
of the superficial horny cells and their continual 
reformation at a deeper level is a process calcu- 
lated to rid the surface of the body of many micro- 
organisms. 

The question whether micro-organisms can ever 
penetrate the unbroken skin has been much dis- 
cussed. Although experiments have shown that 
traumatism is not absolutely necessary, clinical 
experience indicates that these so-called crypto- 
genetic infections are not of ready occurrence. 
When they do occur, the infection atrium is prob- 
ably one of the glandular orifices. 

The sweat glands with their ducts, and the hair 
follicles with their appended sebaceous glands, 
are vulnerable points in the defense which the 
cutaneous surface represents. Although they are 
protected somewhat by the flow of their excretions, 
especially in warm weather, and although the en- 
trance of germs is made more difficult by the con- 
traction of the skin and consequent narrowing of 
the orifices in cold weather, yet various incidents 
may lead to the introduction and retention of 



Cutaneous 
Orifices. 



3G INFECTION AND IMMUNITY. 

virulent micro-organisms in these structures. 
When this occurs there is little difficulty in the 
way of their producing necrosis of the epithelium, 
invading the surrounding tissue and causing a 
pustule, boil, carbuncle, cellulitis, or even a gen- 
eralized infection. The secretion of the sebaceous 
glands appears to.be not germicidal. On the other 
hand, the acid nature and certain salts found in 
perspiration render this fluid antagonistic to the 
development and virulence of certain micro-organ- 
isms. 

The serous exudate, and the crust which forms 
subsequent to an abrasion, antagonize infection. 
The serum itself contains germicidal substances, 
while the crust mechanically prevents microbic 
invasion. 

Soluble poisons such as aconite and bacterial 
toxins are not absorbed through the unbroken skin. 
Sub Connective Even after germs penetrate the epidermis, the 
Tissue, subcutaneous connective tissue is often an obstacle 
to their further extension. The subcutaneous in- 
jection of some micro-organisms (e. g., cholera) 
is tolerated better by animals than one given into 
the abdominal cavity or blood vessels. We are 
also familiar with the benign course of lupus 
compared with visceral tuberculosis; the same is 
true of cutaneous and visceral glanders. This re- 
sistance is explainable, at least in part, by the 
rapidity with which new connective tissue forms 
in the subcutaneous tissue, offering a mechanical 
limitation to the infection, and by the rich lymph 
supply which makes possible the rapid accumula- 
tion of bactericidal lymph and of phagocytic cells. 
On the other hand, it must be mentioned that in 
some diseases the subcutaneous tissue offers no 



SURFACE PROTECTION . 37 

perceptible resistance to bacterial invasion 
(plague) , and that toxins may be more virulent 
when introduced into this tissue than when in- 
jected into the abdominal cavity or the general 
circulation (tetanus). 

The moist condition of mucous membranes has JJ uco h us 
been found to favor the multiplication of many 
microbes, although mucus itself is said to atten- 
uate the virulence of some micro-organisms, as 
the pneumococcus: mucus, however, is not actively 
germicidal. A layer of mucus, on the other hand. 
is a mechanical protection, and its constant excre- 
tion is a means of steadily removing bacteria from 
mucous surfaces. 

The conjunctiva is protected a g- a inst infection Conjunctiva. 
by the mechanical interference of the eyebrows, 
eyelashes, eyelids, irrigation of the conjunctival 
surface by tears which carry germs through the 
lachrymal duct into the nasal cavity, the ability 
of the conjunctival epithelium to repair itself 
rapidly, and the mild germicidal action of the 
salts which are present in the tears. These pro- 
tective agencies, however, are often surmounted 
by micro-organisms, such as the pneumococcus. 
staphylococcus and the influenza bacillus. Many 
soluble poi-ons. aconite, diphtheria toxin and the 
toxin of hay fever are readily absorbed from the 
conjunctiva. 

Compared with the anterior nares. the posterior Nasal 

rrn • ■ n i > Cavitv . 

are poor m micro-organisms. This is no doubt 
due to the filtering of the air by the hairs, the tor- 
tuosity of the channel causing dust and bacteria 
to strike the walls where they are held by a moist 
surface, and the action of the ciliated epithelium 
in carrying them imbedded in mucus, again to- 



38 INFECTION AND IMMUNITY. 

ward the anterior nares. Nevertheless, the rjasal 
mucous membrane is a common infection atrium 
for streptococci, staphylococci, diphtheria and in- 
fluenza bacilli, the diplococcus of epidemic men- 
ingitis, and, probably, for other infectious agents. 

Mouth. At least thirty species of micro-organisms flour- 
ish in the oral cavity, some of them being patho- 
genic: staphylococci, streptococci, pneumococci, 
and often diphtheria bacilli. They are constantly 
removed with the saliva, and through the exten- 
sive desquamation of the epidermis occasioned by 
mastication. Saliva is not germicidal, but in- 
hibits the growth and weakens the virulence of 
some bacteria. The fetid breath and the sor- 
didly observed in fevers where the mouth is dry 
are attributable at least in part to the lack of 
saliva with its anti-infectious properties. The 
great Tapidity with which wounds of the month 
heal is a potent factor in preventing serious infec- 
tions. 

Lungs. Micro-organisms do not 'readily reach the ulti- 
mate ramifications of the bronchioles. In ordinary 
respiration the velocity of the inspired air is so 
reduced as it nears the alveoli that the further 
movements of the gases is one of gradual diffusion 
more than of violent admixture. Consequently 
there are greater opportunities for germ? to come 
in contact with the bronchial walls where they 
become imbedded in mucus with which they may 
be expelled by coughing and the action of the 
ciliated epithelium. Both the alveolar epithelial 
ceils and the leucocytes which enter the air sacs 
and bronchioles have been shown to take up bac- 
teria. The conditions in the lungs which favor 
the development of infections, bronchitis, pneu- 



STOMACH AXD IXTESTIXES. 39 

monia, influenza, tuberculosis, etc., are by no 
means clearly understood. Variations in indi- 
vidual resistance, here as in other parts of the 
bod} T , are certainly of great importance. It is 
probable that the lung is the infection atrium for 
a number of our acute infectious diseases. It has 
been demonstrated that systemic infections, as 
with anthrax bacilli, may be caused by the inhala- 
tion of the germs. 

The gastric juice, through the hydrochloric 
acid it contains, is able to kill anthrax, typhoid, 
tubercle bacilli, cholera vibrio and other organ- 
isms. Clinical and experimental evidence shows 
that this power is often inadequate, virulent 
micro-organisms reaching the intestines in spite 
of it (typhoid, cholera, dysentery, tuberculosis, 
etc.). It is probable that bacteria in the stomach 
are often protected against the action of the gas- 
tric juice to some extent by being imbedded in 
solid particles of food. Certain acidophilic germs, 
as well as yeasts and torulae, seem to flourish in the 
gastric secretions; these are largely non-patho- 
genic, but the regularity with which peritonitis 
follows perforating wounds of the stomach indi- 
cates that it probably always contains pathogenic 
bacteria, though it may be only their temporary 
habitat. The gastric juice may render some bac- 
teria harmless by digesting their toxins; one 
gram of the gastric juice of a dog will neutralize 
fifty fatal doses of diphtheria toxin, or 10,000 of 
tetanus toxin, using the guinea-pig as the test 
animal. On the other hand, the toxin of the bacil- 
lus of botulism (causing a form of meat poison- 
ing) seems to be uninfluenced by the stomach con- 
tents, as the development of the intoxication indi- 



Stomach. 



40 INFECTION AND IMMUNITY. 

cates. Vomiting is often a means of ridding the 
stomach of toxic substances, including bacteria. 
The stomach itself is exceptionally free from in- 
fections. 
intestines. The bile is moderately bactericidal for some 
germs, but, on the whole, the intestinal secretions 
have low germicidal powers; this is indicated by 
the fact that the colon contains many more bac- 
teria than the duodenum. On the other hand, 
the pancreatic juice destroys some- toxin? (diph- 
theria, tetanus) more powerfully even than the 
gastric juice. This ability of the pancreatic juice 
to destroy toxic bacterial products may explain the 
more frequent occurrence of enteritis in the ileum 
than in the duodenum. The bile also has a neu- 
tralizing power for some toxins. Although a num- 
ber of pathogenic bacteria inhabit the intestinal 
tract (colon bacillus, streptococci, etc.), they do 
not often set up inflammatory processes in the 
adult. The tissues, become accustomed to their 
presence. The pathogenic bacteria which do not 
normally exist in the intestines are those which, 
on introduction, are most likely to cause disease 
(typhoid, cholera, dysentery, etc.). The intesti- 
nal tract of the infant, on the other hand, is fre- 
quently attacked by some micro-organisms (strep- 
tococcus, colon bacillus, bacillus pyocyaneu-). 
which in the same locality in the adult appear 
harmless. The fact that many individuals are not 
stricken in an epidemic, in which all are equally 
exposed to infection, points to the probability that 
pathogenic organisms (typhoid, cholera and dys- 
entery) often traverse the intestinal canal without 
inducing disease. Naturally, microbes are elimi- 
nated in enormous quantities in the feces, and in 



INFLAMMATION. 41 

inflammatory states this elimination is increased 
by diarrhea. It is also not to be forgotten that the 
intestinal tract is, to a considerable extent, a 
lymphoid organ, and that consequently in the 
presence of infection enormous quantities of 
phagoc}i:es can quickly be called into action. 

The protective properties of the genito-urinary 
surfaces are not different in principle from those 
already mentioned (vaginal acidity, urinary irri- 
gation). 

B. THE PROTECTIVE NATURE OF INFLAMMATION. 

Although there are many chemical and physical J^J^fJjJ 
agents which may cause inflammation, we are in- 
terested here only in those of an infectious na- 
ture. 

Inflammation may be considered as a reactive 
condition on the part of the tissues, which devel- 
ops in response to the action of some injurious 
agent. The process may be beneficial in some in- 
stances, while in others it may be pernicious from 
the beginning to the end. The thickening of the 
endothelium of the cerebral vessels as one sees it 
in syphilis is a progressive, reactive change which 
in no sense can be of benefit to the individual, and . 
which can have no conceivable function in over- 
coming the syphilitic infection. Likewise, the new 
formed connective tissue seen in alcoholic cirrho- 
sis of the liver is of no benefit to the hepatic tissue, 
though it may serve in some degree to protect the 
liver cells from the alcohol which continues to bo 
ingested. In an ulcer of the cornea the presence 
of serum and of leucocytes, as well as the prolifer- 
ation of connective tissue, may be the sine qua non 
for the healing of the nicer, yet the resulting scar 



42 INFECTION AND IMMUNITY. 

may greatly impair the vision. The inflammation 
in the instances cited is injurious because of the 
functional importance of the tissues involved. On 
the other hand, an extensive scar which has 
formed in tissues of less functional importance,, 
as in the skin and subcutaneous tissue, may be 
harmless. 

It is then to be recognized that there are certain 
consequences of the inflammatory reaction, the 
seriousness of which depends on the situation, 
severity, duration and extent of the process, and 
that these consequences are independent of any 
protective function the inflammation may have 
exercised. 
Variations in The amount and character of the reaction are 

the Reactions. 

subject to many variations, depending on a num- 
ber of conditions: 

1. It varies with the nature of the microbe. 
Non-pathogenic organisms induce little more in- 
flammation than so many minute, inanimate, 
non-toxic particles. The tubercle bacillus causes 
especially the formation of connective tissue, 
giant cells and the accumulation of lymphoid 
cells, aside from some retrogressive changes char- 
acteristic of the disease. ' Organisms similar to 
the streptococcus and pneumococcus lead to the 
formation of pus and fibrin, to the accumulation 
of serum and of polymorphonuclear leucocytes 
more than mononuclears, whereas the prolifera- 
tion of fixed tissue elements is secondary. The 
tetanus bacillus alone causes almost no local in- 
flammatory change. 

2. The reaction is influenced by the virulence 
of a particular bacterium. A streptococcus which 
has lost its virulence is disposed of by the animal 



PHAGOCYTOSIS. 43 

tissues with a minimum tissue reaction, perhaps 
no more than slight congestion and edema and 
the wandering in of a few leucocytes ; one of high- 
er virulence causes an intense reaction, mani- 
fested by congestion, edema, hemorrhages, necro- 
sis and pus formation; then streptococci of such 
great virulence that they destroy life in the course 
of a few hours are occasionally encountered in 
wound infections and in peritonitis, having in the 
meantime elicited a. minimum inflammatory reac- 
tion. 

3. It has a relation to the resistance or the nat- 
ural immunity of the individual. Metchnikoff, 
in particular, has shown that animals of high re- 
sistance to a particular microbe destroy the germ 
quickly by phagocytosis (the ingestion of parti- 
cles bj cells, especially the leucocytes), while in 
susceptible animals the accumulation and activity 
of phagocytic leucocytes are deficient. 

The occurrence of leucocytes in inflammatory Leucocytes. 
conditions is so characteristic that one naturally 
seeks to associate their presence with some in- 
fluence which is exerted by the toxic substance or 
the bacteria which cause the inflammation. It is 
a long-known fact that some microbes attract one 
kind of leucoc}^te, that others attract another 
kind, and that in still other instances the leuco- 
cytes appear to be either uninfluenced or actually 
are repelled by the infecting agent. 

This phenomenon of living cells moving toward chemotaxis. 
or away from certain other cells or substances is 
termed chemotaxis ; the former is positive, the lat- 
ter negative, chemotaxis. There is a somewhat 
general law, but one to which exceptions exist, 
that, regardless of the microbe involved, the more 



44 INFECTION AND IMMUNITY. 

acute the inflammatory process the more do poly- 
morphonuclear leucocytes accumulate, while in 
the more chronic infections, with much connec- 
tive tissue formation, the mononuclear leucocytes 
predominate. Thus in tuberculosis one finds 
lymphocytes and plasma cells — mononuclears — 
predominating greatly over the polymorphonu- 
clears. In the acute purulent infections, on the 
other hand — streptococcus, staphylococcus, pneu- 
mococeus — the latter type of leucocyte predomi- 
nates, the mononuclears being fewer and remain- 
ing at a distance from the center of action. There 
is reason to believe that the mononuclear leuco- 
cytes play an important, though perhaps indirect, 
role in the formation of the connective tissue. 
Phagocytosis. The ingestion of particles by living cells, phago- 
cytosis, is a property which many cells possess. 
Although micro-organisms and inanimate parti- 
cles are sometimes found in epithelial cells, cer- 
tain of the mesoblastic cells have this function 
pre-eminently : Polymorphonuclear leucocytes, 
large mononuclear leucocytes .(lymphocytes), 
ameboid connective tissue and endothelial cells. 
Of these the polymorphonuclear leucocytes, the 
microphages of Metchnikoff, have the greatest 
phagocytic power; the others, the macrophages, 
are more exceptionally phagocytic. Xow. the 
mere ingestion of the bacteria by such cells would 
uot be of necessity injurious to the microbes ; in- 
deed, opponents of MetclmikofFs phagocytic 
theory of immunity hold that phagocvtosis by 
wandering cells may be, and often is. pernicious. 
in that the cells may return to the circulation and 
spread the infection to other parts. But when we 
learn that after ingesting the bacteria the phago- 



PLASMA, SERUM AND FIBRIN. 45 

eytes are often able to kill and digest them, it is 
realized that the process may be a genuine pro- 
tective factor. This being time, the importance of 
positive chemotaxis in recovery from an infection 
becomes manifest. It is also represented that 
phagocytic cells have the power of excreting their 
germicidal substances into the plasma and serum 
and lending to the latter a bactericidal power. 
Furthermore, it is held that they may absorb liquid 
poisons, bacterial toxins, and in some manner de- 
stroy their toxicity. As shown later, these are es- 
sential points in the phagocytic theory of immun- 
ity. 

Serum, even when entirely free of leucocyte-, influence of 
has bactericidal powers; it need not be discussed serum. 
at present whether this power exists primarily in 
the serum or is one conferred on it by the leuco- 
cytes. In view of its presence, however, it is evi- 
dent that the serous exudate which is usually 
present in inflammations, especially the acute, 
may be of influence in combating the infection. 
Serum often contains natural antitoxins, and. in 
addition, it may be of value in lessening the tox- 
icity of poisons by diluting them and aiding in 
their elimination. 

The abundant deposit of fibrin seen in some in- Fibrin. 
flammations is of mechanical value by hemming 
in the infection and in offering a barrier to the 
rapid diffusion of toxins. We are all familiar 
with the part played by fibrinous and fibrous ad- 
hesions in preventing a localized peritonitis from 
becoming generalized. In prolonged inflamma- 
tions fibrin furnishes a ground substance into 
which new connective tissue and vessels grow (or- 
ganization). 



40 INFECTION AND IMMUNITY. 

inflammatory The new formed connective tissue seen in many 
Tissue, inflammations, especially the chronic, as in tuber- 
culosis and actinomycosis, offers an important 
barrier to the extension of an infection. Perhaps 
no better example of this could be cited than the 
dense tissue which forms around a tuberculous 
sinus or abscess. 

To sum up, the inflammatory reaction antago- 
nizes infections, 1, mechanically, through the 
formation of new connective tissue around the 
focus, and dense accumulations of leucocytes and 
fibrin; 2, through the bactericidal and antitoxic 
actions of the lymph and serum; 3, through the 
phagocytic action of ameboid cells. 

The value of hot applications in local inflam- 
mations, in that they increase congestion, which 
hastens the exudation of plasma and leucocytes 
and the proliferation of cells, finds a logical ex- 
planation in view of the facts mentioned. Also 
increase in local temperature probably favors 
chemical actions. The special features of the 
phagocytic theory of immunity are considered in 
a later chapter. For many details in regard to 
inflammation, the reader is referred to the classic 
article of Adami on this subject in the first vol- 
ume of Allbutt's System of Medicine. 

C. THE ANTIBACTERIAL AND THE ANTITOXIC 
NATURE OF NATURAL IMMUNITY. 

In a previous page it has been stated that nat- 
ural immunity may be either antibacterial or anti- 
toxic. We have seen that the protection afforded 
by the body surfaces may be effective against both 
microbes and their toxins, and that local inflam- 
matory processes, although most certainly antago- 



NATURAL ANTIBACTERIAL IMMUNITY. 47 

nizing ihe bacteria, may at the same time have 
some antitoxic value. 

The term natural immunity, however, as indi- Natural . , 

■" ' Antsbactenal 

cated in the first chapter, has a peculiar applica- immunity. 
tion to the natural resistance of some species or 
races of animals to infections to which other spe- 
cies or races are susceptible ; and to an unusual in- 
dividual resistance often seen in members of a 
given race or species. This condition depends on 
properties residing in the tissues or fluids of the 
body, and consequently is independent of any pro- 
tection which the body surfaces afford. Its pres- 
ence is demonstrated in the most striking man- 
ner by the experimental method, when microbes 
or toxins are injected directly into the tissues or 
circulation. At the same time every-day observa- 
tion provides many examples. 

In determining the antibacterial nature of im- 
munity in a given case there are two conditions 
which must be proved: 1, that the body cells or 
fluids are able to destroy the microbe, and that 
this power is sufficiently strong to make it reason- 
able that the immunity depends on it; 2, that the 
immunity does not depend on non-susceptibility 
to a possible toxin of the microbe, nor on a nat- 
urally existing antitoxin. 

To prove the first condition, three procedures 
may be resorted to : First, the microbes are in- 
jected into the subcutaneous tissue, the peritonenl 
cavity or the blood vessels. If the animal doe- 
not become ill after a dose which, in proportion to 
weight, is pathogenic for some other test animal, 
an immunity is indicated. At a proper interval 
all the tissues and fluids are examined to deter- 
mine the fate of the microbes. This may be clone 



48 INFECTION AND IMMUNITY. 

by staining the fluids and cells for bacteria and 
examining with the microscope, or by inoculating 
culture tubes with the fluids, the growth or non- 
growth of colonies determining whether or not the 
microbes have disappeared. Examinations of this 
nature often disclose the fact that many of the 
bacteria have been phagocytized by the leucocytes,, 
while others have apparently succumbed to the 
germicidal action of serum or plasma. It is often 
desirable to determine the extent to which mi- 
crobes are eliminated through the excretions 
(urine or feces) ; this is best clone by the culture 
method, but is a difficult technical problem. 

Second, the animal's serum or plasma may be 
mixed with a suspension of the microbes in a 
number of test tubes, using varying amounts of 
serum with constant amounts of the bacteria in 
the different tubes, and at a subsequent period, 
from three to twenty-four hours later, cultures 
are made from these mixtures to determine the 
bactericidal power of the serum. The numbers of 
colonies which appear in these cultures, minus the 
number which appear when serum is not added, is 
an index of the bactericidal power of the serum . 
If this power is found to be high, it is, in the pres- 
ent state of our knowledge, considered as pre- 
sumptive evidence that the natural immunity of 
the animal depends on it. It is, nevertheless, a 
fact that the antibacterial immunity of an animal 
does not always go hand in hand with the bac- 
tericidal power of its serum. A well-known illus- 
tration of this is the following: Both the dog and 
the rat have a rather high degree of immunity 
against infections with the anthrax bacillus: yet 
it has been found that the serum of the dog has 



NATURAL ANTITOXIC IMMUNITY. 49 

almost no bactericidal effect on this microbe, while 
that of the rat has a very strong effect. At the 
same time we should remember that the bacterici- 
dal power of the serum does not necessarily repre- 
sent the entire antibacterial function of the body. 
In the serum we have none of the body cells, and 
especially none of the phagocytes, the destructive 
action of which on some bacteria is well known. 

Third, it is now possible to perform test-tube 
experiments with the leucocytes of an animal, 
whereby the phagocytic power of these cells for a 
given microbe may be determined. This may be 
done by counting in stained specimens the num- 
ber of bacteria which are englobed; or the bac- 
tericidal power of the leucocytes may be deter- 
mined approximately by performing the culture 
experiments described in the preceding paragraph, 
in this instance, however, substituting fresh defib- 
rinated blood for the serum. If the bactericidal 
power of the defibrinated blood (containing leu- 
cocytes) is greater than that of the serum alone, 
the effect of the leucocytes becomes apparent. 
This receives further consideration in the chapter 
on phagocytosis. 

At a time when the antitoxic action of serums Alexins, 
was not appreciated, Buchner gave the name of 
alexins (from the Greek, Skifriv, to ward off) to 
the protective substances of the serum, i. e., to the 
bactericidal substances, making the observation 
that they were very labile substances, losing their 
power spontaneously in a few days when exposed 
to the air and light, or when they were heated to 
55 C. for thirty minutes. 

In determining the presence or absence of anti- Natural. 
toxic immunity, the toxin of the microbe, of immunity 



50 INFECTION AND IMMUNITY. 

course, must first be in hand. The methods of ob- 
taining toxins will be referred to later. If the 
animal resists a dose of toxin which, in proportion 
to weight, produces disease in some other suscepti- 
ble animal, the tissues or fluids of the first animal 
may contain antitoxin. It will be indicated later 
how this result may be obtained even without the 
presence of antitoxin, the immunity being due to 
some other obscure cause. If the resistance is 
referable to the presence of antitoxin, the latter 
may be detected in the following manner: The 
animal is bled, its serum collected from the clot, 
then mixtures of the serum and of the toxin are 
injected into animals of known susceptibility for 
the* toxin. If the test animal is in this way pro- 
tected from an otherwise fatal dose of the toxin, 
it is evidence that the serum contains an antitoxic 
substance. 

Following this method of experimentation, if 
antibacterial properties are found to the exclusion 
of antitoxic, the immunity is considered to be an- 
tibacterial ; and with the converse result it is anti- 
toxic. It is, of course, conceivable that in a given 
case it might be both antitoxic and antibacterial. 
In dealing with diseases of which the specific mi- 
crobe is known and cultivated, the existence of 
antibacterial or of antitoxic substances can usual- 
ly be found by the methods described. If the eti- 
ology is unknown, as in scarlet fever, measles, 
syphilis, etc., that is, if the virus and its toxin can 
not be obtained in quantities, the nature of the 
resistance is not at present open to determination. 

Examples are known in which, in spite of 
rather high resistance on the part of the animal, 
its serum contains neither strong antitoxic nor 



NON-SUSCEPTIBILITY. 51 

bactericidal properties. This relationship exists 
between a number of animals and such bacteria 
as the pneumococcus, staphylococcus and strepto- 
coccus. It is possible that the phagocytes are im- 
portant factors in immunity to these infections. 

It is seldom that natural resistance is absolute. 
Pasteur found that the great immunity of the 
chicken for anthrax could be overcome by im- 
mersing the animal in cold water, the reduction 
in body temperature supposedly decreasing the re- 
sistance. It was stated in a previous chapter that 
physical exhaustion, hunger and exposure to cold 
may also reduce natural resistance. Pestilence 
and famine often go hand in hand. 

Similarly, antitoxic immunity usually is rela- jjjjjjjjj 
tive. The chicken, which withstands a large quan- 
tity of tetanus toxin when injected into the skin, 
muscles or circulation, succumbs when the toxin 
is injected directly into the nervous tissue. As 
an illustration of natural immunity to toxins, 
the following table serves a good purpose. The 
horse is the most susceptible animal for tetanus 
toxin. If the minimum fatal amount for one gram 
of horse weight is taken as a unit, this scale of re- 
sistance for some other animals is obtained 
(Knorr) : 

For 1 gram of guinea-pig weight 2 units are fatal 

For 1 gram of goat weight 4 units are fatal 

For 1 gram of mouse weight 13 units are fatal 

For 1 gram of rabbit weight 2,000 units are fatal 

For 1 gram of chicken weight 200,000 units are fatal 

In view of the high immunity of the chicken tu/imv* cep 
against tetanus, one may be led to suppose that its 
serum would contain a large amount of antitoxin, 
yet experiments show that it possesses practically 
no tetanus antitoxin. This fact suggests that 
there is a distinct type of natural immunity 



52 



INFECTION AND IMMUNITY. 



Cell 
Receptors, 



Importance of 
the Tissue 
Attacked. 



which, it is thought, may be independent of both 
the antibacterial and the antitoxic properties of 
the body. 

It is now thought that the toxic elements of bac- 
teria are chemical substances (very complex, 
surely) which are able to injure the tissues, i. e., 
to cause disease, only by entering into chemical 
union with substances which the cells contain. 
Such chemical substances of groups pertaining 
to the cells will be referred to later under the 
name of cell receptors. Accordingly, if the cells 
of an animal do not possess groups or receptors 
which are capable of forming a chemical union 
with the toxin, the latter would be unable to pro- 
duce injury, i. e., the animal would be immune 
even in the absence of all bactericidal or antitoxic 
properties. This condition, however, is not one 
which is capable of experimental demonstration, 
at least at present, but the conditions point irre- 
sistibly to its existence in some cases. 

We are accordingly led to the conclusion that 
immunity to toxins is not in all cases antitoxic, 
in the sense that the serum contains demonstrable 
antitoxin; and likewise that immunity to bacteria 
is not in all cases antibacterial, in the sense that 
the serum contains substances which are able to 
kill the bacteria in test-tube experiments. Non- 
susceptibility and phagocytosis may be of impor- 
tance in resistance of this type. 

There is another factor, however, which may 
throw light on the type of natural immunity just 
considered. We know that tetanus toxin causes 
tetanus through its power of uniting with the 
nerve cells, and we may consider that tetanus is 
a very fatal disease, primarily because of the vital 



SUMMARY. 53 

nature of the tissue which it attacks. Now, if the 
toxin, instead of uniting with the cells of a vital 
organ, were to combine with cells of less impor- 
tance to the economy, as, for example, the cells 
of the subcutaneous tissue, it is probable that we 
should have no tetanus. In some of the lower ani- 
mals there is reason to believe that the toxin of 
tetanus does unite with such tissue (Metchnikoff ) .- 
Eoux and Borrel believe that the greater degree of 
immunity which the rabbit has over the guinea- 
pig is due largely to the fact that the rabbit's 
liver is able to fix a great deal of the toxin. And 
Metchnikoff has found that the liver of the scor- 
pion, which has an absolute immunity to tetanus, 
absorbs the toxin and retains it for months. 

By way of summary, then, we may say that the Summary. 
natural blood immunity and tissue (histogenic, 
Behring) immunity depend on the following fac- 
tors: Bactericidal and antitoxic powers of the 
serum and plasma, the destructive effect of the . 
cells, especially the phagocytes, on both bacteria 
and toxins; a possible absolute non-susceptibility 
in some cases (the absolute non-existence of suit- 
able cell receptors) ; the overwhelming distribu- 
tion of the suitable receptors for the toxin in or- 
gans of less vital necessity for the individual, thus 
diverting it from more important organs. 

In order that a pathogenic organism produce a 
progressively fatal disease in a susceptible animal, 
the following obstacles must be surmounted : The 
strong defenses of the body surfaces must first be 
overcome; a local inflammatory reaction which 
may have been excited must first prove itself to be 
inadequate for the limitation of the infection; 
there must be an insufficient supply or insufficient 



54 INFECTION AND IMMUNITY. 

activity of antimicrobic and antitoxic processes in 
the body fluids and cells. 

In view of the wide variations in the nature of 
different infections agents, it is possible that the 
defensive means which would counteract one 
might be inadequate for another; and inasmuch 
as animals appear to differ as much in the charac- 
ter of their defensive as microbes do in their of- 
fensive powers, there is abundant room for the 
display of the various phenomena of natural im- 
munity and of natural susceptibility with which 
we have become familiar. 

OTHER PROPERTIES OF NORMAL SERUMS. 

Hemolysis. j n addition to the bactericidal and antitoxic ac- 
tion of many normal serums, they often possess 
other characteristics which are of the highest in- 
terest in the study of immunity. In earlier clays 
it had been noted that the transfusion of blood 
from one species to another was often fatal to the 
injected animal. Later investigations showed 
that this was due to toxic substances in the trans- 
fused blood; substances which, above all, de- 
stroyed the red blood cells of the injected animal. 
This action, in which the hemoglobin is dissolved 
out of the red blood cells, may be reproduced in 
test-tube experiments by mixing the blood cells of 
one animal with the serum of another which is 
toxic (e. g., rabbit blood + goat serum). This is 
the phenomenon of hemolysis, and the appearance 
of such a tube is exactly like that seen when blood 
is mixed with distilled water or even with tap 
water; i. e., it is a laking of the blood, it loses its 
opacity and assumes a beautiful cherry-red color. 
The serum of practically every species contains a 



HEMOLYSIXS, ETC. 



55 



hemolytic substance (a serum hemolysin) for 
some kind of erythrocyte. 

Some serums also contain toxic agents for other Cytotoxins. 
cells; they are generally called serum cytotoxins. 
The serum of the eel not only contains a strong 
hemolysin, or hemotoxin, but also a powerful 
poison for nervous tissue, neurotoxin. Similarly 
we have normal leucotoxins for leucocytes, nephro- 
toxin for kidney tissue, etc. 

Another property of many normal serums is Agglutinins. 
that which causes agglutination or clumping of 
bacteria, as one sees it in the Gruber-TTidal test 
for typhoid. Even normal human serum may ag- 
glutinate the typhoid bacillus, but to a less degree 
than that of a typhoid patient. 

One serum often causes a precipitate in the Precipitins. 
serum of another animal, or in a bacterial culture 
filtrate. 

In considering these facts, one becomes con- 
scious of the great complexity of that substance 
which plays so important a part in immunity and 
its study — i. e., the blood serum. 



CHAPTEE VI. 



ACQUIRED IMMUNITY. 

Immunity which is acquired as the result of 
infection is said to have been acquired naturally, 
a very different thing from natural immunity. 
Immunity which is acquired artificially may be 
active, as in vaccination; or passive, as when 
diphtheria antitoxin is injected prophylaetically. 
Active One who has recovered from scarlet fever, small- 
pox, plague, typhoid fe^er, etc., becomes possessed 
of lasting protection against subsequent attacks. On 
the other hand, the immunity afforded by an at- 
tack of certain other diseases usually -is of shorter 
duration: cholera, diphtheria, pneumonia., etc, So 
far as known, the acquired protection is very spe- 
cific in character: e. g., a person who has had 
measles may still have scarlet fever; or an attack 
of cholera does not protect against a later attack of 
typhoid. 

In a number of diseases one attack confers no 
evident protection against a second; gonorrhea, 
influenza, recurrent fever and malaria. Some dis- 
eases may create a predisposition for recurrence: 
erysipelas, influenza, diphtheria in some instances, 
although a natural susceptibility of the individual 
may explain repeated attacks. 

A very important factor for progress in artifi- 
cial immunity was the knowledge that even a light 
attack of an infection (scarlet fever, cholera, 
typhoid, smallpox) may be efficient in conferring 
immunity. Such light attacks are frequently 
noted sporadically and in epidemics, while occa- 
sionally an epidemic is mild in character through- 



VACCINATION. 



57 



out. An epidemic of benign smallpox recently 
prevailed in the middle Western states and the 
mild character of the plague which was endemic 
in San Francisco will be remembered. In these 
instances it seems probable that the mild charac- 
ter of the disease depends on the low virulence of 
the organism which causes the epidemic; and the 
condition suggests the possibility of artificial at- 
tenuation of virulent micro-organisms for the pur- 
pose of inducing at will infections of a benign 
character. 

It might be possible to so modify the virus that vaccination. 
protection could be established without setting in 
motion the actual disease even in a mild form. 
An attenuation of this nature had long been prac- 
ticed with smallpox virus. Before cowpox was 
resorted to as a source of vaccine, it had been the 
custom to inoculate the genuine virus of smallpox, 
for the purpose of producing immunity. Con- 
trary to the natural expectation, this method, 
instead of reproducing severe smallpox, often 
caused the modified disease which we call 
varioloid. This phenomenon may depend on the 
fact that the virus finds the skin' and subcutaneous 
tissue an unfavorable medium for the development 
of virulence; a condition which would be equiva- 
lent to an attenuation of the microbe. The patho- 
genicity of the cholera vibrio in animal experi- 
ments is affected similarly in subcutaneous injec- Attenuation. 
tions. It is now generally considered that cowpox 
is smallpox which has suffered a decrease in viru- 
lence because of its passage through the cow. 
Consequently, when this weakened virus is planted 
in the skin of man, where it may undergo further 
attenuation and produce the mildest possible form 
of modified smallpox, we have an ideal vaccine. 



58 INFECTION AND IMMUNITY. 

Passage. In a similar manner the virulence of the anthrax 
bacillus for sheep may be lessened by passing the 
organism through the dove. This method of de- 
creasing, or in some cases of increasing, the viru- 
lence of a micro-organism is known as passage. 

No single method of attenuation is suitable 
for all organisms. Pasteur found that cultures 
of the bacillus of chicken-cholera become so weak- 
ened when exposed to the action of light and air 
that they may safely be used as vaccine; also that 
the anthrax bacillus when grown at 42° C. is at- 
tenuated and does not form spores, and conse- 
quently becomes a suitable vaccine for sheep and 
cattle. Of no less interest to us is Pasteur's 
method of attenuating the virus of hydrophobia 
by desiccating the spinal cords of infected ani- 
mals (rabbits) ; the altered cords are then suitable 
for the immunization of individuals who have 
been bitten by a rabid animal. 

Work of the past decade has shown that suc- 
cessful vaccination is possible against cholera, 
typhoid and plague by the inoculation of aviru- 
lent cultures, or those which have been killed out- 
right by heat. In so far as we know the immunity 
which iis caused by vaccination or protective in- 
oculation is antibacterial, or, better, antimicrobic. 
If the cause of the disease is unrecognized, as in 
smallpox and hydrophobia, there is no means of 
determining whether it is antibacterial or anti- 
toxic. 

Nature of One may ask if acquired immunity to bacteria 
immunity, and to toxins is due to the presence of the anti- 
bacterial and antitoxic substances which were 
mentioned in connection with natural immunity. 
Although normal serum is strongly bactericidal 



LEUCOCYTES. 59 

for the typhoid bacillus, the serum of one who has 
recovered from typhoid fever possesses this power 
to a much greater degree. As this is true in many 
other bacterial infections, the new resistance is 
held to depend on the increase of bactericidal sub- 
stances in the serum. Similarly in acquired im- 
munity to diphtheria and to tetanus, the most 
conspicuous change is a great increase in the cor- 
responding antitoxins. The result is the same, 
regardless of whether the immunity be produced 
by a natural attack of the disease, or by artificial 
immunization with the specific microbe or toxin. 
Accordingly it seems probable that acquired im- 
munity in these instances depends on the presence 
in the serum of an increased amount of properties 
which, to a certain degree, may be present nor- 
mally. 

It was stated in the section on natural immun- The Leucocytes 
ity that the leucocytes, acting as phagocytes and immunity. 
as resorptive cells, seem to be responsible, at least 
in part, for natural resistance to an infection. 

Metchnikoff and his followers have provided us 
with many observations which are interpreted as 
showing that the importance of these cells is con- 
tinued into acquired immunity. These investiga- 
tors state that in acquired immunity the phago- 
cytes have a much greater capacity for ingesting 
and killing bacteria and for absorbing and de- 
stroying toxins than when the animal is in a state 
of greater susceptibility. It is also concluded that 
the serum in active immunity owes its new or 
more powerful antibacterial, antitoxic and other 
properties to the leucocytes, which under the in- 
fluence of the infection have overproduced and ex- 
creted these substances into the plasma. 



60 



INFECTION AND IMMUNITY. 



Passive 
Immunity. 



The Leucocytes 
in Passive 
Immunity. 



It will appear later that recover}' from certain 
infections (streptococcus, staphylococcus, pneumo- 
coccus, etc.) is not characterized by the formation 
of antibacterial or antitoxic substances. In these 
instances it seems probable that the temporary 
immunity, of which recovery is the outward mani- 
festation, is due to destruction of the bacteria by 
phagocytic cells. This conception seems all the 
more plausible when we remember the hyperleu- 
cocytosis which characterizes these- infections. 

Inasmuch as it has proved possible by the pro- 
longed immunization of animals with bacteria or 
toxins to induce a high concentration of antibac- 
terial or antitoxic substances in. their serum, it 
was the natural expectation that if such serums 
were injected into other animals the latter would 
thereby be endowed with an increased resistance 
to the infectious agent against which the serum 
had special activities (passive immunization). 
This has been found to be the case with many 
antibacterial (typhoid, cholera, plague, dysentery, 
etc.) and some antitoxic serums (diphtheria, teta- 
nus). Unfortunately the protection afforded by 
the injection of an immune serum is of short dura- 
tion (from two to several weeks) ; it is as if a for- 
eign substance had been injected, the fate of which 
is to be eliminated rapidly. This is in contrast 
to the condition in active immunity in which the 
protective substances are often formed over a long 
period by the body cells. 

The school of Metchnikoff brings the leucocytes 
into relation with passive as well as active im- 
munity. It is held that the immune serum which 
is injected is potent, because it stimulates the leu- 
cocytes to a greater phagocytic activity in the case 



BACTERIOLYTIC EXZY2IES. 61 

of antibacterial i minimi t} T , or to a greater absorp- 
tion and destruction of toxins in the case of anti- 
toxic immrmity. 

Our knowledge of poisons (see Chapter XIV) opsonins. 
is as yet so limited that positive statements can not 
be made as to the part they play in acquired im- 
munity, although it is thought that immunization 
with some microbes causes an increase in the 
quantity of opsonins. 

Mention may be made here of the well-known 
but curious phenomenon that resistance may vary 
with the age of the individual. Typhoid fever at- 
tacks the adolescent or middle-aged rather than 
the very young or very old. Active tuberculosis 
grows less common in the later decades of life. 
Then we have what are distinctively the diseases 
of childhood: after 15 years of age diphtheria, for 
example, is uncommon. Some of these instances 
of acquired immunity may be referable to differ- 
ences in the character of the cell receptors at dif- 
ferent ages, while perhaps others are due to a slow 
immunizing process occasioned by the prolonged 
presence of non-pathogenic amounts of the proper 
micro-organisms. 

Emmerich and Loew found that many bacteria Bacteriolytic 
produce in culture media, as well as in the animal 
body, substances which apparently act as ferments 
and which are able to kill not only the bacterium 
which secretes the ferment, but many others. For 
example, pyocyanase, the bacteriolytic enzyme of 
Bacillus pyocyaneus, dissolves pyocyaneus, 
anthrax, diphtheria and typhoid bacilli, the vibrio 
of cholera, the streptococcus and staphylococcus. 
These enzymes usually are not toxic, and it is sup- 
posed that during the course of an infection they 



Enzymes. 



G2 



INFECTION AND IMMUNITY. 



Immune 
Cytotoxins. 



Immune 
Agglutinins. 



reach such a concentration in the blood that they 
destroy the bacteria which produced them, thus 
bringing about recovery. It is claimed also that 
they, either during infection or as a result of re- 
peated injection of the ferment, enter into- a some- 
what permanent combination with the albumin of 
the body, forming the so-called "immune-pro- 
teidin," on which acquired immunity depends. 

It is also stated that with "pyocyanase-immune- 
proteidin" it is possible to so immunize a rabbit 
that a subsequent (12 days) otherwise fatal dose 
of the anthrax bacillus is harmless. 

Although the effects of these "enzymes" on 
anthrax and on some other organisms have been 
confirmed by a number of investigators, their im- 
portance in acquired immunity and in the recov- 
ery from infections is very doubtful. There is the 
special objection to this theory that it puts im- 
munity on a non-specific basis; i. e., pyocyanase 
will protect against anthrax, diphtheria, etc., 
while, in reality, all our clinical and experimental 
data point to the high specificity of acquired 
immunity. 

The serum acquires antibodies not only for bac- 
teria and toxins, but also for many other cells and 
substances which may be used for immunization. 
There are many immune cytotoxins, such as the 
serum hemolysins, leucotoxins, neurotoxins, 
nephrotoxins, etc., which are formed as the result 
of immunization with the corresponding cells. 
(See Chapter XIII.) 

By systematically injecting an animal with a 
bacterium or with any tissue cell, agglutinating 
substances (the agglutinins) are formed and may 
be demonstrated in the serum. Like other anti- 



PRECIPITINS. C3 

bodies, they are highly specific for the cell used in 
the immunization. (See Chapters IX and X.) 

It has been found that toxins, other than those 
of bacterial origin, will yield antitoxins by im- 
munization. Such toxins are snake venom, yield- 
ing antivenin; ricin, a hemagglutinating toxin 
from the castor oil bean, yielding antiricin, etc. 

Eecently what is termed the biologic test for p)!™" n j|j ns 
species has assumed prominence. This test may and 
be illustrated: A goat is injected repeatedly with Test for 
the serum of man. After a number of injections 
a very minute amount of this goat's serum will 
cause a precipitate when mixed with human 
serum, but not when mixed with the serum of any 
other animal (except, perhaps, that of anthropoid 
apes). The test is so delicate that when a small 
amount of old dried human blood is dissolved in 
salt solution and treated with the goat serum the 
precipitation will still occur, and in view of this 
fact, the test has become of medicolegal impor- 
tance. The wide distribution of this phenomenon 
among all kinds of animals gives it great biologic- 
significance. 

Kraus found that by immunization with cer- 
tain bacterial filtrates substances are formed in 
the serum which cause precipitates in the filtrates. 
It is further interesting that other albumin-con- 
taining substances, as egg albumin or milk, will 
on immunization, yield specific antibodies. The 
serum of an animal which has been immunized 
with goat's milk will cause a precipitate in the 
latter, but not in cow's milk. (See Chapter 
XI.) 

It has also been possible to obtain specific anti- ^ n t^ erments - 
bodies for ferments : for the peptonizing ferments 



64 INFECTION AND IMMUNITY. 

of bacteria, for emulsin, lab, fibrin ferments, etc. 
There are, however, very many substances for 
which serum antibodies can not be obtained; this 
is true for all substances of known chemical com- 
position, as acids, bases, salts, and for the alka- 
loids (strychnin, morphin, aconite, etc.) 



CHAPTER VII. 



TOXINS AND ANTITOXINS. 

Through Ehrlich the word toxin has come to Ehriich's 
have a special significance, being applied only to a of Toxin. 
certain type of toxic substances. Toxins have the 
following properties (Ehrlich) : 

1. They are extremely labile substances which 
occur as secretion products of vegetable or of ani- 
mal organisms.. 

2. Their chemical nature is unknown. The im- 
possibility of obtaining them in pure form and 
their great lability render them insusceptible to 
ordinary chemical analysis. 

3. An analysis of a toxin may be reached at 
present only through the medium of animal ex- 
periments. 

4. Immunization with toxins yields antitoxins. 
It has not been possible to obtain antitoxins for 
inorganic poisons, glucosids and alkaloids 
(morphin, strychnin, etc.) 

5. In contrast to well-defined chemical poisons, 
the action of toxins is characterized by a latent or 
incubation period. That is, following the introduc- 
tion of a toxin, a certain period of time elapses 
before toxic symptoms appear, and this period is 
greater than the time logically required for the 
absorption of the toxin through the circulation. 1 

The incubation period may be shortened experi- 

1. Recent work indicates that the long incubation period 
of tetanus may depend, at least in part, upon the length 
of time required for the toxin to reach the ganglion cells 
through the axis cylinders of the motor nerves. 



Preparation 
of Toxins. 



66 INFECTION AND IMMUNITY. 

mentally by the injection of large quantities of 
toxin, but it can not be eliminated entirely. Snake 
poison appears to act without incubation period, 
but it is still to be classed with the toxins, because 
of its power to cause the formation of an anti- 
toxin. 

6. "The facts make it necessary to assume, as a 
condition for the poisonous action of toxins, a spe- 
cific chemical union of the toxin with the proto- 
plasm of the cells in certain organs." . . . "The 
affinity of other poisons, as the alkaloids, for 
tissues, depends not on chemical union, but on 
some such process as solid solution or loose salt 
formation." 

The preparation of soluble toxins is relatively 
simple. It is necessary only to inoculate a suitable 
fluid culture medium with a culture of the micro- 
organism, to allow growth to take place for some 
da}rs at body temperature, then to pass the fluid 
through a porcelain or some equivalent filter. The 
soluble toxins usually may be precipitated from 
the filtrate by some precipitant, as ammonium 
sulphate, and preserved in a dried state for a long 
period. Such a precipitate does not represent the 
toxin in a pure form, but various proteid sub- 
stances of the culture medium, as well. 

The bacilli of diphtheria and tetanus Bacillus 
pyocyaneus, and Bacillus botulismus, are the princi" 
pal micro-organisms which produce soluble toxins. 

When the toxins of these organisms are injected 
into a suitable animal, phenomena similar to those 
produced by an infection with the organisms 
themselves are produced. They are in a particu- 
lar sense specific toxins. Some micro-organisms, 
however, produce more than one toxin. The teta- 



MULTIPLICITY OF TOXINS. 67 

nus bacillus, for example, secretes, in addition to 
the toxin causing the nervous symptoms of tetanus, 
another (tetanolysin, or tetanus hemolysin) which 
has the power to destroy red blood cells, Ehrlich 
holds that the diphtheria bacillus produces not 
only the toxin which causes the acute intoxication 
of diphtheria, but another of long incubation 
period which may cause paralysis. Cobra poison 
has at least two toxins, one which attacks the nerv- 
ous tissues' — a neurotoxin — and another which at- 
tacks the erythrocytes; the two may be separated 
by appropriate measures. As previously stated, 
the serum of the eel has a strong neurotoxin and 
a hemotoxic. 

Some micro-organisms produce one or more Secondary 
soluble toxic substances, which it is often difficult 
or impossible to consider as the actual disease- 
producing elements of these organisms. Concern- 
ing a disease which is so well characterized clini- 
cally as tetanus, it is not difficult to determine 
by inoculation experiment whether one has in hand 
the specific toxin. The proof is naturally much 
more difficult in relation to streptococci and 
staphylococci, for example, where the group of 
symptoms and the pathologic conditions are not 
entirely unique for the infection. We are by no 
means certain that the hemolysin or the leucoci- 
din (toxin for leucocytes) of the staphylococcus, 
or the hemolysin of the streptococcus are the para- 
mount disease-producing toxins of these organisms, 
although these substances are true toxins. 

An important test for the pathogenic signifi- 
cance of a toxin lies in its ability or inability to 
cause the formation of an antitoxin which is 
efficient in the treatment of an infection by the 



68 



INFECTION AND IMMUNITY. 



Intracellular 

Toxins, or 

Endotoxins. 



The McFadyen 
Method. 



corresponding organism. This is not the case 
with the toxins just mentioned. However, one 
should not place too much importance on such a 
test, for it is quite possible that we are not able on 
artificial culture media to obtain the toxin in 
such concentration that the production of an effi- 
cient antitoxin is possible. 

There is a large class of organisms the members 
of which apparently do not produce soluble toxins ; 
such organisms, however, cause highly toxic diseases 
(e. g., typhoid, cholera, plague). The dead or 
ground-up bodies of such bacteria are very toxic; 
also when the germs disintegrate by a process of 
autolysis or self-digestion the culture medium be- 
comes toxic because of the cell contents which are 
set free. Such organisms are said to contain in- 
tracellular toxins or endotoxins. In infections by 
them it is supposed that toxic symptoms are pro- 
duced when a pathogenic amount of the intracel- 
lular toxins is liberated by the bacteriolytic action 
of the body fluids or cells (phagocytes). 

Nothing is known of the nature of such toxins. 
The}^ certainly are very different from the soluble 
toxins of diphtheria and tetanus, since immuniza- 
tion with them has not as yet resulted in the pro- 
duction of efficient antitoxins. In spite of this 
fact, however, it is none the less probable that 
they are the disease-producing constituents of the 
organisms. Buchner gave the name of "plasmin" 
to the cell juice which he was able to express from 
some micro-organisms. 

McFadyen, by grinding large masses of typhoid 
bacilli which had been rendered brittle by the tem- 
perature of liquid air, obtains from this organism 
a toxic cell juice. The efficiency of the antitoxin 



PREPARATION OF ANTITOXINS. 69 

which he is said to obtain b} r immunization with 
this material has not been demonstrated practi- 
cally. It seems improbable that immunization 
with this "toxin" will yield a serum differing in 
properties from that obtained by immunization 
with the living organisms. 

Toxic substances obtained- from bacteria by the Accidental 

, • n • t Toxic Sub- 

action of strong chemicals and extracting fluids, stances. 
may not represent the essential toxic substance of 
the organism, but perhaps some disintegration 
product which happens to be toxic. 

It is, of course, common knowledge that an anti- 
toxin is the blood serum of an animal, after the 
latter has been rendered highly immune by re- 
peated injections of the corresponding toxin. The 
horse is chosen for immunization because of its 
marked ability to 'yield antitoxins (diphtheria, 
tetanus), because of its size, withstanding much 
loss of blood, and because of the readiness with 
which it submits to manipulation. 

Manufacturing plants which produce antitoxins Preparation 

,., .. , x .... . of Antitoxins. 

and other antiserums on a large scale have splen- 
didly equipped stables, which are kept in the 
maximum hygienic condition, and from which rats 
in particular are rigorously excluded. 2 The horses 
are carefully groomed and fed and given such ex- 
ercise as will keep them in a healthy condition. 
The toxins, in solution, are injected subcutane- 

2. The importance of this is very great if, for example, 
horses are receiving injections of some virulent living 
micro-organism (as the plague bacillus). In this case 
living micro-organisms reach the general circulation, and a 
rat having bitten the animal could well contract the 
plague and be an evident source of danger, not only to 
other animals, but to the community at large. Even fly- 
proof stalls are properly instituted in such cases. 



Attenuation 



70 INFECTION AND IMMUNITY. 

ously. 3 Grave and even fatal reactions may follow 
the first injections, if the toxin has been given in 
too large doses or in too concentrated solutions. 
This is especially true when injecting tetanus 
toxin. It is of great importance first to establish 
what the Germans call a "Grundimmunitat" 
which means a primary immunity in the animal 
itself so that the immunization may then be 
pushed vigorously until the blood contains anti- 
toxin in high concentration. For this purpose it 
has been found necessary to weaken the first tox- 
ins injected. This may be done by heating the 
"of Toxins" toxin solution to 65 or 70 C. for an hour; by add- 
ing to it from 0.05 to 0.4 per cent, of the trichlo- 
rid of iodin; or by adding a solution of potassium 
iodid in which iodin has been dissolved (LugoFs 
solution). High dilutions of the unaltered toxin 
may also be used. Gradually the virulence and 
amount of the toxin injected may be increased 
until finally the full virulent toxin is given in 
large doses. The increase in dosage must be very 
gradual. Eventually as much as a liter or more 
of diphtheria toxin is tolerated. 

Following each injection a reaction occurs. 
With diphtheria the local swelling may be great, 
and sloughing may occur. Following an injection 
of tetanus toxin, tetanic symptoms may appear. 
In either case, there is some loss of weight and 
often fever, and another injection must not be 
given until the original weight is regained and 
the general behavior of the animal indicates that 
its former healthy condition is re-established. 
Several months of such treatment are necessary 

3. For the production of antivenin the snake venom Is 
best injected intravenously. 



PRESERVATIVES. 71 

for the production of diphtheria antitoxin in high 
concentration. At the end of this time blood is 
drawn from the jugular vein by means of a large 
trochar to which a rubber tube is attached. The 
tube leads to a tall glass c}iinder holding from 
one to two liters, and into this the blood is allowed 
to now. Six liters may be drawn safely from a 
horse of average size. 4 The most Tigid asepsis is 
observed in taking the blood. The glass cylinders, 
appropriately covered to prevent contamination, 
are then set in a cool, dark place, and after the 
serum has separated from the clot samples are 
taken to be tested for their antitoxic value. 

The serum, in bulk or after being bottled for £f e s S e r r ums!, ves 
the trade, is preserved at a low temperature and 
in the dark, 0.5 per cent, of carbolic acid having 
been added to insure sterility. The addition of 
the acid may cause harmless cloudiness in the 
serum, but does not destroy the antitoxin. Serums 
may be preserved perfectly in a dried or frozen 
state. 

Many facts of scientific and practical impor- 
tance have been brought to light through the im- 
munization of animals on a large scale. It has 
been found, for example, that following each in- 
jection of toxin the amount of antitoxin in the 
blood suffers a reduction, and only equals, or rises 
above the previous amount eight or ten days later. 
This decrease is explained by assuming that the 
toxin has, to a certain extent, united chemically 
with the circulating antitoxin. It indicates also 



4. Some horses may be bled as many as forty times 
without suffering a conspicuous deterioration in health. 
In time, however, an animal becomes less valuable as an 
antitoxin producer. 



72 • INFECTION AND IMMUNITY. 

the period at which the horse should be bled in 
order that the greatest amount of antitoxin may 
be obtained. It might even be dangerous to draw 
the blood before this time had elapsed, since some 
free toxin might still be in the circulation. 

It is noteworthy that all horses are not equally 
good producers of antitoxin. One may yield a 
serum of three times the value of another, al- 
though the two have been treated identically and 
seem to be equally immune to the toxin. 

Another most interesting fact is that, although 
the 1 blood of an animal may be very rich in anti- 
toxin, he still may have a disproportionate sus- 
ceptibility to fresh injections of the toxin. 

Many of these phenomena have not been ex- 
plained satisfactorily. 
standardize- The necessity of standardizing antitoxins so 
and Antitoxins, that dosage may be controlled accurately is self- 
evident. To meet this need the antitoxic unit 
familiar in practice was devised. 

Behring, and also Ehrlich, decided arbitrarily 
to consider as the antitoxic unit that quantity of a 
serum which would protect a guinea-pig from 100 
fatal doses of the toxin. Ehrlich's original method 
of testing a serum was to mix different quantities 
with 10 fatal doses of the toxin and inject each 
mixture into a guinea-pig of 250 to 300 grams' 
weight. That quantity of the serum which pro- 
tected the animal against the ten fatal doses of 
toxin contained 1/10 of an immunity unit, and 
from this result the number of units in a cubic 
centimeter could be calculated. This method in- 
volved the use of toxin as the standard by which 
the value of the antitoxin was measured, and it 
was found to be unreliable. A toxin degenerates 



ANTITOXIC UNIT. 73 

rather rapidly, retaining at the same time its 
binding power for the antitoxin; hence two tests 
made with the same serum two months apart 
might indicate different antitoxic values for the 
serum. Also 10 fatal doses of one toxin often re- 
quired more antitoxin for neutralization than the 
same quantity of a second toxin. These phenomena 
are due to the formation of toxids. (See next 
chapter. ) 

On account of these sources of error, Ehrlich 
devised a new method in which a standard anti- 
toxin or test-serum is used as the starting point 
for the valuation of a new serum. The test-serum standard 
used at the Royal Prussian Institute for Experi- 
mental Therapy at Frankfurt, of which Ehrlich 
is the chief, is a dried and powdered serum of 
such strength that 1 gram contains 1,700 immun- 
ity units; i. e., 1/1700 of a c.c. would protect a 
guinea-pig against 100 fatal doses of a diphtheria 
toxin. 5 Any other high-grade serum would have 
answered equally well. 

The institute keeps in stock a large number of 

5. In Germany the various serums are prepared by pri- 
vate individuals or corporations and manufacturers are re- 
quired to send a sample of every lot of serum intended for 
the trade to the Frankfurt Institute that its exact value may 
be determined. Each bottle eventually receives a stamp sig- 
nifying the value in antitoxin units of the contained serum. 
Moreover, samples of every lot of serum are retained in the 
institute, and from time to time these are tested ; and when 
it is found that the samples have degenerated beyond a cer- 
tain value the order is sent out to call in all serum belong- 
ing to the degenerated lot. When a manufacturer thinks 
the serum of one of his horses has a high value he may 
draw a small amount of blood from the animal and send 
the serum to Frankfurt for a preliminary test. If the 
serum is sufficiently strong he may then bleed the hors a 
freely ; if it is weak he will be advised to continue th. 1 
immunization for a time. 



74 INFECTION AND IMMUNITY. 

vials, each containing two grams of this dried 
serum. The air and moisture are exhausted from 
each vial and the latter is then sealed in the name. 
Once in three months one of these vials is broken 
open carefully and the serum dissolved in 200 c.c. 
of a solution made up of equal parts of glycerin 
and 10 per cent, salt solution; hence each cubic 
centimeter of the solution contains 17 units. Dur- 
ing the succeeding three months this antitoxic 
solution is used in the comparative valuation of 
new antitoxins ; the solution retains ' its strength 
unaltered for this period. For' individual tests 
the serum-solution just described is again diluted 
seventeenfold, so that each cubic centimeter con- 
tains one unit. This adds to convenience and ac- 
curacy. 

The first step in the process is to standardize 
some diphtheria toxin in which the degenerative 
changes (toxoid formation) have come to a stand- 
still. This is done by adding so much of the toxin 
to 1 unit (1 c.c.) of the test serum that an excess 
of one fatal dose of the toxin remains unbound by 
the antitoxin. 

The quantity of the toxin which gives this re- 
sult is called the L+dose. 6 The LO dose of the 
toxin also is determined, this being the amount 
which is exactly neutralized by the unit of anti- 
toxin. The use of the two doses serves to eliminate 
subjective errors on the part of the observer. The 
L-f and LO doses of toxin are then used to de- 
termine the value of new antitoxins. That quan- 
tity of the new serum which, when mixed with the 
L+ dose of toxin, causes the animal to die in 

6. L=Limes (Limit) ; + is commonly used to indicate 
a fatal result. 



NATIONAL REGULATIONS. 75 

four to six days, contains 1 unit of antitoxin. If, 
for example, 1/100 c.c. accomplishes this result, 
the serum is of one hundredfold strength i. e., 1 
c.c. would contain 100 antitoxic units. 

For therapeutic purposes, it is desirable to have 
a serum of high value in order to avoid giving too 
large quantities. Several diphtheria serums are 
on the market which have a value of 500 units to 
the cubic centimeter. It is difficult to immunize 
above this point. 

In addition to the need of knowing the exact Purity of 

° Serum. 

antitoxic value of a serum, it should be determined 
positively that there is no contamination of the 
serum, and especially that no adventitious toxin 
(tetanus) is present. 

The sterility of the serum is determined by both 
aerobic and anaerobic cultures, and its freedom 
from toxins by injecting considerable quantities 
into animals. The serum should not have more 
than 0.5 per cent, of carbolic acid as a preserva- 
tive. A convenient method of determining this 
point is the injection of 0.5 c.c. of the serum into 
a white mouse. If more than this quantity of the 
acid is present the mouse dies. 

Similar principles prevail in the standardiza- 
tion of tetanus antitoxin, the mouse being used as 
the test animal. Unfortunately tetanus antitox- • 
ins practically go without standardization in this 
country. This would seem to be for commercial 
reasons only, for they may be standardized with a 
low percentage of error. 

That the United States government is attempt- 
ing to guard the quality of diphtheria antitoxins 



76 INFECTION AND IMMUNITY. 

on sale in our markets is apparent from the fol- 
lowing statement: 7 

•'EXAMINATION OP SERUMS MADE BY LICENSED 
MANUFACTURERS. 

"The act of Congress, approved July 1, 1902, entitled 
'An act to regulate the sale of viruses, serums, toxins and 
analogous products in the District of Columbia, to regulate 
interstate commerce in said articles, and for other pur- 
poses,' and the regulations framed thereunder, approved 
Feb. 21, 1903, imposed upon the director of the Hygienic 
Laboratory the duty of examining vaccines and antitoxins 
for purity and potency. 

"Accordingly purchases are made for the Hygienic Lab- 
oratory from time to time on the open market by officers 
of the Public Health and Marine-Hospital Service stationed 
in various parts of the country. The antitoxin is always 
bought from reliable druggists, who keep the product under 
proper conditions of light, temperature, etc. Several grades 
of diphtheria antitoxin made by each licensed manufac- 
turer are bought and sent to the Hygienic Laboratory by 
mail for the purposes of these tests. 

"The serums are tested not only for potency, but also to 
determine their freedom from contamination by foreign 
bacteria, and finally to insure the absence of chemical poi- 
sons, especially tetanus toxin. Note is made of the phys- 
ical appearance of the serum, and tests are made to de- 
termine whether an excessive amount of preservative has 
been added. 

"A careful memorandum is made of the facts given by 
the manufacturer, as stated on the label, as to the num- 
ber of units contained in the package, and the date beyond 
which the contents can not be expected beyond a reasonable 
doubt to yield a specific result. Note is also made of the 
manufacturer's compliance with the law requiring that the 
product be plainly marked with the name of the article, 
and the name, address and license number of the manu- 
facturer. 

"Delinquencies that occasionally come to light in these 
examinations are at once reported to the Surgeon General. 
U. S. Public Health and Marine-Hospital Service, who 

7. Taken verbatim from Rosenau, "The Immunity Unit 
for Standardizing Diphtheria Antitoxin," Bulletin No. 21 of 
the Hygienic Laboratory of the Public Health and Marine 
Hospital Service of the United States. M. J. Rosenau is 
Director of the Hygienic Laboratory. 



OFFICINAL ANTITOXIN. 77 

takes the necessary steps requiring the immediate with- 
drawal of the particular lot of serum from the market and 
institutes measures to prevent a repetition of similar errors." 

'SERUM ANTIDIPHTHERICUM IN THE PHARMA- 
COPEIA. 
•'The next edition of the United States Pharmacopeia, 
being the eighth decennial revision, 1900, which is to ap- 
pear shortly, will contain an antitoxic serum for the first 
time. The serum will be known officially as antidiphtheric 
serum or Serum antidiphthericiim, and the unit will be 
recognized as that approved or established by the United 
States Public Health and Marine-Hospital Service. 

"The official text, which has been kindly furnished by 
Professor Remington in advance, will be as follows : 
"SERUM ANTIDIPHTHERICUM. 

A.XTIDIPHTHEEIC SERUM. DIPHTHERIA ANTITOXIN. 

"A fluid separated from tbe coagulated blood of a horse 
Equus caballuSj Linne, immunized through the inoculation 
of a diphtheric toxin. It should be kept in sealed glass 
containers, in a dark place, at temperatures between 4.5° 
and 15° C. (40° and 59° F.). 

"A yellowish or yellowish-brown, transparent or 
slightly turbid liquid, odorless or having a slight odor, 
due to the presence of the antiseptic used as a pre- 
servative. 

"Specific gravity: 1.025 to 1,040 at 25° C. (77° F.). 
"Antidiphtheric serum gradually loses its power, the 
loss in one year varying between 10 per cent, and 30 
per cent. Each container should be furnished with a 
label or statement, giving the strength of the anti- 
diphtheritic serum, expressed in antitoxic units, the 
name and percentage by volume of the antiseptic used 
for the preservation of the liquid (if such be used), 
the date when the antidiphtheric serum was last tested, 
and the date beyond which it will not have the strength 
indicated on the label or statement. 

"The standard of strength, expressed in units of anti- 
toxic power, should be that approved or established by 
the United States Public Health and Marine-Hospital 
Service. 

"Average dose : 3\000 units. 

"Immunizing dose for well persons : 500 units." 



CHAPTER VIII. 



Biologic 
Analysis 



Neutralization 

of Toxin by 

Antitoxin. 



THE STRUCTURE OF TOXINS AND ANTITOXINS 
AND THE NATURE OF THE TOXIN-ANTI- 
TOXIN REACTION. 

Because of the impossibility of obtaining bac- 
terial toxins in pure form, no conception can be 
gained of their composition in terms of atoms or 
molecules, although it is convenient to assume 
that they have some unknown molecular struc- 
ture. Inferences as to their nature and structure 
can be gained only by means of the biologic ex- 
periment, i. e., their effects on animals and animal 
cells under arbitrary conditions. 

When a toxin and its antitoxin are mixed in 
suitable proportions, the mixture becomes non- 
toxic as the result of chemical union of the two 
substances; each molecule of toxin has combined 
with a molecule of antitoxin to form a new non- 
toxic molecule which may be spoken of as the 
toxin-antitoxin molecule. It was at one time sup- 
posed that antitoxin had the power of destroying 
the toxin, perhaps by a ferment-like action. In 
two instances it has been possible to show that 
this is not the case. Ordinarily toxins are more 
susceptible to heat than antitoxins, but in the case 
of pyocyaneus toxin and snake venom the anti- 
toxins are the more susceptible. Wasserman 
found that when a neutral mixture of pyocyaneus 
toxin and its antitoxin was heated to a certain 
temperature the mixture again became toxic, and 
Calmette made a similar observation concerning 
venom and antivenin. If the toxin had been de- 



TOXIX-AXTITOXIX REACTIOX. Id 

stroyed by the antitoxin the solution certainly 
would not have regained its original toxicity on 
the application of heat. 

The following facts add support to the view chemical 
that neutralization consists of chemical union be- Reaction. 
tween -fehe two substances : 

First, neutralization takes place according to 
the law of multiple proportions, i. e., ten times a 
given amount of antitoxin will neutralize a pro- 
portionate amount of toxin; second, neutralization 
is more rapid at warm than at cold temperatures ; 
and, third, more rapid in concentrated than in di- 
lute solutions. These are some well-known laws of 
chemical reactions. 

"Emil Fischer has shown that in the ferments, Ferments. 
definite atom-groups of special configuration are 
present which above all else are requisite for the 
whole phenomenon (of fermentation). Only such 
substances as possess a group to which the ferment 
group corresponds, as lock to key, are subject to 
the action of a particular ferment." This applies 
to the action of a particular ferment on only one 
kind of substance. 

Having this conception in mind, Ehrlich as- Haptophores 
sumes that union occurs between toxin and anti- 
toxin through a special group of atoms which the 
toxin molecule possesses, and which fits into, or 
corresponds specifically to, another group of atoms 
in the antitoxin molecule. These are spoken of 
as the binding or haptophorous groups (hapto- 
phores) of the molecules. The haptophorou? 
group of the toxin molecule is highly specific since 
a toxin can be neutralized only by its own anti- 
toxin, and naturally the haptophorous group of 
the antitoxin molecule must be equally specific. 



80 INFECTION AND IMMUNITY. 

Toxophore. The toxin molecule contains not only a hapto- 
phorus group, through which it unites with anti- 
toxin in one instance or with tissue cells in the 
production of disease, 'but also certain constituents 
in which the specific activity of the substance re- 
sides. Toxin is able to work a change in tissue cells 
after it has combined with them. The toxic prop- 
erty is said to reside in a toxophorous group. The 
toxophorous and haptophorous groups are parts of 
the toxin molecule. 
Toxoids. It is a peculiarity of toxins that they lose a cer- 
tain amount of their toxicity in the course of time, 
although their binding power for antitoxin remains 
practically unchanged. In the language of the 
terms which were used above, the toxophorous 
groups may degenerate or disappear and leave the 
haptophorous groups intact. Toxins which have 
undergone this change are called toxoids. 

Further evidence of the existence of toxoids lies 
in the fact that when used for immunization they 
cause the formation of antitoxins. This is possi- 
ble only when the substance is able to unite with 
the tissue cells; therefore, the non-toxic toxin or 
toxoid has retained its haptophorous groups. 

A toxin entirely free from toxoids has never ■ 
been observed, since even during the few days re- 
quired for its preparation a certain amount of 
degeneration occurs. 
Partial Additional information concerning the nature 

Method of of toxin has been gained by experimenting with 
mixtures of toxin and antitoxin, in which the two 
are present in varying proportions. This is the 
"partial saturation" method of Ehrlich. Through 
a vast number of experiments Ehrlich obtained in- 



"TOXIX SPECTRUM." 81 

formation which permitted him to estimate that 
200 "binding units" are represented in that 
amount of diphtheria toxin (Irypo the tically pure) 
which is exactly neutralized by one antitoxin unit. 
If the entire amount of antitoxin., i. e., 200/200, 
is added to the quantity of toxin in question, com- 
plete neutralization of the latter, of course, occurs. 
In case the toxin is entirely pure, 199/200 of the 
antitoxin unit would destroy all but 1/200 of the 
initial toxicity; and 150/200, or 100/200, or 
75/200, etc., of the antitoxin when added would 
permit corresponding degrees of toxicity to be 
demonstrated through animal inoculations. It 
was found, however, that neutralization did not Jo ^. n 
take place according to this simple scale. The re- Spectrum. 
suits were complicated, and Ehrlich has found it 
convenient to express them graphically in the form 
of a "toxin spectrum" (Figs. 1, 2, 3 and 4). For 
example, let 199/200 of the antitoxin unit be 
added to the proper amount of the toxin, 198/200 
to another similar amount, 197/200 to another, 
etc., down to 150/200. In the last mixture, 50 
out of the 200 binding units which the toxin pos- 
sesses are free, and these 50, rather than some Epitoxoids. 
other 50, are free because they have less affinity 
for the antitoxin than the 150 units which were 
bound. It has been found that those units which 
first become free have a low degree of toxicity. It 
was thought that they might have lost their toxo- 
phorous groups, i. e., that they were toxoids ; and 
because of their weak affinity for antitoxin they 
were called epitoxoids. It was found, however, that 
they possessed a rather constant though low degree 
of toxicity and that the toxic action was characteris- 



82 INFECTION AND IMMUNITY. 

tic. Injection was followed by some local edema, 
Toxon. t nen by a long incubation period, and finally by 
cachexia and paralysis. On account of this char- 
acteristic toxic action and the long incubation 
period, Ehrlich has concluded that the so-called 
epitoxoid is in reality a second toxin which is se- 
creted by the diphtheria bacillus. This he now 
designates as toxon 1 in order to distinguish it from 
that other constituent of diphtheria bouillon, the 
toxin, which causes the acute phenomena of diph- 
theria. 
Protoxoids. .Jjq^ ne now ac ~i c j s tiH smaller amounts of the 
antitoxin unit to the 200 binding units of the 
toxin. When 149/200 are added it is found that 
a certain amount of true toxin remains free, the 
quantity which is unbound being in direct propor- 
tion to the amount of antitoxin withheld. Conse- 
quently when but 50/200 antitoxin unit is added 
the amount of free toxin corresponds to 100 bind- 

1. The existence or non-existence of toxons has created 
a great deal of discussion among investigators. The Swed- 
ish chemist, Arrhenius, has recently attempted to apply 
certain principles of physical chemistry to the study of 
toxins and antitoxins. It is a well-known fact that some 
chemical substances, when in solution, have the power of 
breaking iip into their constituent parts ; thus sodium 
cblorid breaks up in part into sodium and chlorin, as so- 
dium or chlorin ions or electrolytes. The dissociated so- 
dium or chlorin may then enter into combination with any 
other suitable substances which may be present. Arrhenius 
holds that this is the case with the toxin-antitoxin molecule, 
thai: it may to a certain extent again break up into sep- 
arate toxin and antitoxin. He believes that this dissociated 
toxin is the substance which Ehrlich has been calling 
toxon. Madsen, who formerly had done much work with 
toxons. has now joined with Arrhenius in support of the 
dissociation theory. In spite of the reasonableness of this 
theory, Ehrlich and his followers continue to uphold the 
toxon as an Independent toxic substance, and have pub- 
lished additional experiments to support their position. 



PROTOTOXIXS, ETC. 



83 



ing units. If true toxin only remained it could 
then be said that the constitution of this toxin is : 
toxin 150 and toxon 50. However, it may be 
found that as 49/200, 48/200, etc., to 0/200 anti- 
toxin unit are added, no increase of free toxin is 
found, although the antitoxin added has been 
bound. In this case, the 50 binding units of toxin 
which have the greatest affinity for antitoxin are 
non-toxic; i. e., they are toxoids, and since they 
have the maximum affinity for antitoxin they are 
called protoxoids. 

It has been assumed also that a toxoid may 
exist which has an affinity for antitoxin exactly 
equaling that which toxin possesses; this, as yet 
purely hypothetical constituent, bears the name of 
svntoxoid. 

Figure 1 is a graphic representation of the 
toxin just described (Madsen) . Probably no two 
toxins have the same constitution. The toxon 
zone, for example, could well be much larger in 
one diphtheria toxin than in another. 

Refinements in experimentation show that even 
the true toxin is not uniform in its virulence and 
its affinity for" antitoxin. Accordingly a proto- 
toxin, a deuterotoxin and a tritotoxin may be rec- 
ognized by this same partial saturation method. 
(See Fig. 2.) For example, it may be found that 
when a portion of the antitoxin unit, between the 
limits of 149/200 and 125/200. is withheld, a 
toxin is left free which is less virulent than that re- 
maining free between the limits of 124/200 and 
100/200 ; and from this point on the new unbound 
toxin may be still more virulent. The first would 
be tritotoxin, the second deuterotoxin and the 
third prototoxin. 



Syntoxoids. 



Proto-, 
Deutero- and 
Tritotoxins. 



84 



INFECTION AND IMMUNITY. 



'ProtoUxoid 




oxone 



— \ — i — i ■ v \ — f t • t ' t v ' > ■' * » ■ ■ - v •} i — ■ — r— r- 

4 /o *o so yo jo i» to to 9* i*o i/o txo no in /«•& Ho no it* /ft *»q 
Figure 1. 




Proton* i ti . JDeutno- Tri to toxin 
toxt-n , 

Figure 2. 

_. Heutero- n+ + • ., 




PrtCoToxi* £ toutero- Tf itoToxtn /9 
toKcn> /9 

Figure 3. 



Prototoxoid 0^eutcro iX Trito toxaidfr a 



oxone 




Beutero- TritoToxtn 



Figure 4. 
Figures 1, 2, 3 and 4 are taken from Aschoff's "Ehr- 
lich's Seitenkettentheorie, etc.," Ztschr. f. Allgem. Physiol., 
vol. i, 1902. Figure 1 is a toxin spectrum worked out by 
Madsen. Figures 2, 3 and 4 are spectra representing the 
changes in qualitative and quantitative structure which a 
toxin may undergo with age, as described in preceding para- 
graphs. 



ORIGIN OF ANTITOXIN. 85 

The "spectrum" of a toxin changes with its age. 
The prototoxin, and portions of the deutero- or 
tritotoxin m^ disappear because of toxoid forma- 
tion. Such changes have led to the recognition of 
an alpha and a beta modification of the toxin. 
The alpha modifications of all three toxins readily 
become toxoids. Only the beta modification of the 
deuterotoxin remains constant: The toxon also 
remains relatively intact (Figs. 2, 3 and 4). 

This very complicated method of investigation 
was also undertaken by Madsen in the study of 
tetanus toxin, for which a somewhat similar 
"spectrum" was constructed. 

Such spectra have not been worked out in de- 
tail for some of the vegetable toxins, as ricin and 
abrin, but it is known that they form toxoids. 

Snake venom differs from the bacterial toxins 
in structure (See Part II, Chapter III). 

The idea was originally advanced that antitoxin The Formation 
was transformed toxin, a change in the latter hav- 
ing been effected through some action of the 
tissues. In that case, the amount of antitoxin pro- 
duced should be roughly equivalent to the amount 
of toxin injected. This, however, was found not 
to be the case. A single injection of tetanus toxin 
may yield 100,000 times the amount of antitoxin 
.necessary to neutralize the toxin injected. An in- 
teresting experiment is on record which shows the 
fallacy of the view just mentioned. An animal, 
the serum of which was rich in antitoxins, was 
bled repeatedly until an amount of blood which 
equaled the total quantity normally present in the 
animal's body was drawn. Yet the antitoxic 
power of the new formed blood was practically un- 
changed. 



86 



INFECTION AND IMMUNITY. 



Ehrlich's 

'Side-Chain" 
Theory. 



Receptors. 



Multiplicity 
of Receptors. 



Metchnikorr, to explain this "overproduction" 
of antitoxin, has suggested that the toxin molecules 
may be taken up by phagocytic cells and broken up 
into an indefinite number of smaller molecules, 
each of which then is altered in some obscure man- 
ner so as to constitute a molecule of antitoxin. 

The views of Ehrlich have found wide accept- 
ance, and have provided a valuable working hy- 
pothesis for many investigations. A considera- 
tion of this subject introduces one at once to the 
well-known side-chain theory of immunity of 
Ehrlich. It may be considered briefly at this point, 
in so far as it involves the origin and nature of 
antitoxin. Ehrlich considers it fundamental, in 
regard to the metabolic activity of cells, to assume 
that the cell constituents must enter into chemical 
combination with food substances in order that the 
latter may be made available for the use of the 
cell. It is supposed that cells contain cer- 
tain atom groups of unknown chemical nature 
which make possible the binding of food sub- 
stances. The name of receptor was given to such 
groups, since substances are received into the cell 
through them. Inasmuch as the foods and some 
other substances which penetrate the cells differ 
in their chemical nature, it is probable that there 
are various receptors for the various types of sub- 
stances. The binding, however, is but a prelimi- 
nary step to profound changes which the substance 
may next undergo, through the action of other, 
more vital, cell constituents. That is to say, the 
receptor is but a link to bring the substance into 
relationship, with the vital activities of the cell, 
which Ehrlich supposes may reside in a hypotheti- 
cal "Leistitngd'crn' (action center or nucleus). 



ACTION OF TOXINS. 



87 



III view of this conception one readily understands side-chains. 
the propriety of considering the receptor as a side- 
chain of the "Leistungskcm" just as the chemist 
speaks of the various groups which may be at- 




Fig. 5. — Graphic representation of receptors of the first 
order and of toxin uniting with the cell receptor, a, Cell 
receptor ; ft, toxin molecule ; c, haptophore of toxin mole- 
cule ; d, toxophore of toxin molecule, e, haptophore of the 
cell receptor. From Ehrlich's "Schlussbetrachtungen," 
Nothnagel's System of Medicine, vol. viii. This cut is not 
to be taken as representing the actual morphology of toxins 
or cell receptors. Nothing is known of their morphology, 
if, indeed, they have any. The cut is intended merely to 
represent, in a graphic manner, the supposed chemical 
structure and mode of action of these substances. This 
statement applies also to Figures 6 and 7. 

tached to the benzol ring, or benzol nucleus, as 
side-chains (See Chapter XV). 

In preceding pages it has been emphasized that Action of 
a toxin, in order that it may injure a cell, must 
enter into chemical combination with its constitu- 



88 INFECTION AND IMMUNITY. 

ents, and it is a fundamental tenet of the Ehrlicli 
theory that this union is one which takes place 
between the toxin and a cell receptor (side-chain). 
The cell receptor, then, either is a haptophore or 
possesses a haptophore as a part of its complex. 

As the physiologic demands are probably re- 
sponsible for the character of the various recep- 
tors, it is not likely -that special receptors are 
created when some unusual substance, as a bac- 
terial toxin, is introduced into the body. Conse- 
quently, when toxin unites with a cell, it probably 
occupies receptors which, under normal circum- 
stances, are employed in some physiologic process. 

If some inert, non-toxic substance should com- 
bine extensively with cells, a corresponding num- 
ber of receptors, which ordinarily are used for 
normal metabolism, would be thrown out of func- 
tion. Union of this nature would be equivalent 
to an injury of the cell, and it is possible "that the 
action of toxoids is of this mild nature. 

When toxin unites with cells there is involved 
not only the diversion of cell receptors from their 
customary functions, but in addition the destruc- 
tive action of the toxin on the vital parts of the cell 
(perhaps on the "Leistungskern"). The more 
toxin introduced, the greater the number of cell 
receptors bound, and the greater the injurv to the 
cell. 
Hypothesis In case a non-fatal amount of toxin has been 
bound, but sufficient to cause some injury, how 
does the cell respond to the injury? Weigert, a 
few years ago, gave expression to a hypothesis 
which is held to have some bearing on this ques- 
tion. In studying regeneration following injury 
he concluded that tissues have the tendencv to 



STRUCTURE OF ANTITOXIN. 89 

reproduce not only to the extent of making good 
the injury, but that an excess of new tissue re- 
sults. The clearest example of this occurrence is 
that of scar formation, in which a seeming excess 
of new connective tissue cells is formed, . 

which later disappears in part. Similarly, when of side-chains. 
a non-fatal amount of toxin unites with the 
receptors, a cell defect or injury is created. The 
cell has for practical purposes lost so many recep- 
tors. This loss affects the vital activities of the 
cell, the "Leistungskem" and new receptors, iden- 
tical with those occupied, are reproduced. Follow- 
ing the law stated, they are reproduced in excess 
of the number injured, and the excess may be so 
great that the cell may be overfilled with them — 
so overfilled that many are discharged and reach 
the general circulation. These cast-off receptors, 
or side-chains, still retaining their power of unit- 
ing with toxin, constitute our antitoxins. As 
Behring has stated it, the receptor, when attached 
to the cell, is the argent through which the latter 
is attacked, but when cast off from the cell becomes 
its protector (Fig. 5). 

As regards the structure of the antitoxin (cast- Receptors of 

«, , N ., . , -i it the First Order. 

on receptor), it is necessary to assume only the 
presence of the proper haptophorous group. Ehr- 
lich designates all receptors of this simple type as 
"receptors of the iirst order." In following 
sections we will have to do with receptors of the 
second and third orders. 

Wassermaim gives the following list of anti- 
toxins : 

ANTITOXINS FOR BACTERIAL TOXIN'S. 

Diphtheria antitoxin. 
Tetanus antitoxin. 



90 INFECTION AND IMMUNITY. 

Botulism antitoxin. 
Pyocyaneus antitoxin. 
Symptomatic anthrax antitoxin. 
Antileucocidin, an antitoxin for the leucocytic 

poison of the staphylococcus. 
Antitoxins for the blood dissolving toxins of a 

number of bacteria. 

ANTITOXINS FOR ANIMAL TOXINS. 

Antivenin for snake poison. 
Antitoxin for scorpion poison. 
Antitoxin for spider poison. 
Antitoxins for certain poisons of fish, eel serum, 
salamander, turtle, and for wasp poison. 

ANTITOXINS FOR PLANT TOXINS. 

Antiricin, for a red blood corpuscle poison of 

the castor oil bean. 
Antiabrin, for a similar poison of the jequirity 

bean. 
Antirobin, for robin, a locust tree poison. 
Anticrotin, for crotin, a toxin from the bean of 

Croton tiglium, the croton oil bean. 
Hay fever antitoxin, for the toxin of pollens 

which cause hay fever. 

ANTIFERMENTS. 

Antirennet. 
Antipepsin. 
Antitrypsin. 
Antifibrinferment. 

Antiurease, for urease, a urea splitting ferment. 
Antilaccase. 
Anti tyrosinase. 
Antisteapsin. 

Antiferments against the ferments of bacterial 
cultures. 



OTHER ANTITOXINS. 91 

The above axe true antitoxins. There are other 
substances, however, which occasionally exert an 
antagonistic action on toxins, although they prob- 
ably are not true antitoxins. For example, it has 
been found that cholesterin neutralizes the action 
of tetanolysan, the hemolytic toxin of the tetanus 
bacillus. 

The discovery of Hektoen that certain salts are 
able to neutralize the toxic action of some serums, 
by combining with the so-called complement, may 
also be mentioned in this connection. 



CHAPTER IX. 



Wide! and 
Grunbaum. 



THE PHENOMENON OF AGGLUTINATION. 

Agglutination, in the bacteriologic sense, refers 
to the clumping and sedimentation of a homogene- 
ous suspension of micro-organisms by the action of 
a serum. 
specificity. Although a number of investigators had ob- 
served the phenomenon of agglutination, Gruber 
and Durham first saw its significance. They found 
that the reaction was a specific one, i. e., that the 
serum which would cause the strongest agglutina- 
tion of a micro-organism was that of an animal 
which had been made immune to it by repeated 
injections. 

WidaFs service consisted in the utilization of the 
phenomenon as an aid in the diagnosis of typhoid 
fever. He is the originator of clinical serum 
diagnosis. It is perhaps largely a matter of acci- 
dent that we speak of the Widal reaction rather 
than the Grunbaum reaction. Grunbaum was car- 
rying on the same work at the same time, but 
Widal preceded him in the publication of his more 
extensive work. 

In the chapter on natural immunity it was 
stated that normal' serums, often are able to ag- 
glutinate bacteria. Normal human serum may ag- 
glutinate the typhoid, colon, pyocyaneus, and dys- 
entery bacilli, and occasionally the staphylococcus 
and cholera vibrio; it does not agglutinate the 
streptococcus and some other organisms. In cer- 
tain cases it may agglutinate the typhoid bacillus 



Normal 
Agglutinins. 



NORMAL AND IMMUNE AGGLUTININS. 



93 



even when the serum is diluted to one in thirty, a 
point of practical importance in the clinical use of 
the test. When a normal serum is found to have a 
high agglutinating power, a previous infection by 
the micro-organism is to be thought of. This pos- 
sibility receives emphasis from the fact that the 
serum of a new-born child is devoid of many of the 
agglutinins which are found in later life. Hence, 
of the so-called normal agglutinins, man)^, after 
all, may be acquired properties. 

The term immune agglutinin is applied to the 
agglutinating substance in a serum, when the 
property has developed as a result of infection, or 
of systematic immunization with the organism. 
They are formed during infections with the organ- 
isms of typhoid, cholera, dysentery, plague, etc. 

For the artificial production of agglutinins, the 
bacteria may be injected into the veins, subcutane- 
ous tissue, or peritoneal cavity; in some cases they 
may be fed to animals, rubbed into the skin, or 
sprayed into the lungs. If certain micro-organ- 
isms are sealed up in a collodion sac and placed in 
the abdominal cavity of an animal, an agglutinat- 
ing serum will be formed ; the necessary substances 
diffuse through the sac and reach those body cells 
which produce the agglutinin. It is not necessary 
that living bacteria be injected ; in fact, the strong- 
est agglutinin is said to be formed by the injection 
of bacteria which have been killed by a tempera- 
ture of 62 C. In certain instances agglutinins are 
produced by immunization with disintegration 
products of bacteria or with bacterial extracts. 

Nearly all bacteria, even when non-pathogenic, 
will give rise to agglutinating serums when in- 
jected ; but not all have the power equally. Nicolle 



Immune 
Agglutinins. 



Agglutinin 
Producing 
Organisms. 



94 INFECTION AND IMMUNITY. 

and Trenell distinguish three groups of bacteria 
in regard to their agglutinability by the homolo- 
gous antiserums. 1 The first group includes easily 
agglutinable organisms, for the most pathogenic: 
Typhoid, dysentery, cholera, plague, glanders, and 
the colon, psittacosis, pyocyaneus bacilli, and B. 
enteritidis. They yield agglutinating serums read- 
ily either as a result of infection or by immuniza- 
tion. The second group comprises organisms 
which, during infection or convalescence, do not 
cause the formation of agglutinins, but may be 
forced to do so by systematically injecting them 
into animals. In the third group are included 
those which, even during prolonged immunization, 
rarely cause the formation of agglutinating 
serums: the Friedlander bacillus. These facts 
may be taken as an index of the diseases in which 
we may expect to obtain the agglutination reaction 
by the serum of the patient. 
variations m The degree of agglutinating power which may 
Power of be obtained hj immunization varies greatly. Van 
rgamsms. ^ er Velde speaks of a typhoid serum which in a 
dilution of one in one million was agglutinating, 
and Durham had a cholera serum which was ef- 
fective in a dilution of one in two millions. Such 
powerful serums are rarely obtained. 

Even two different strains of the same organism 
may differ in their ability to cause the formation 
of agglutinins. It is generally said that a typhoid 
strain, which is agglutinated with difficulty, gives 
rise to a weak agglutinating serum, while an easily 

1. The homologous organism for a typhoid serum, for ex- 
ample, is the typhoid bacillus, and vice versa ; other organ- 
isms, or other serums, are heterologous. These are commonly 
used terms. 



DISTRIBUTION AND VARIATIONS. 



95 






agglutinable strain gives a strong agglutinin. The 
logic of this will become apparent when we con- 
sider the' nature of the bacterial substance which 
causes the body to produce agglutinin. 

That the agglutinating power of the serum of a Variations in 

i. -j 4.- % ■ 1 P j i • 47 j. Quantity of 

typhoid patient varies irom day to day is a fact Agglutinin. 
of practical importance. It may be thirty times as 
strong one day as the next, and may even disap- 
pear entirely for a day or two. Hence the impor- 
tance of making more than one test in a suspicious 
case, when the first trial has been doubtful or 
negative. There is no adequate explanation for 
this great variation. It is said that mixed infec- 
tions, intestinal hemorrhage, or a sudden pouring 
out of typhoid bacilli into the circulation may 
cause a reduction in the agglutinating power. This 
occurrence has an important bearing on the possi- 
bility of using the agglutinating power of the 
serum as a prognostic sign. Although it has often 
been noted that in fatal infections agglutinins may 
be absent from the serum, the variations just men- 
tioned indicate that prognosis could not be based 
safely on the result of a single agglutination test. 
The agglutinating substance is found in the 
highest concentration in the blood serum, but it 
may be demonstrated in the various body fluids 
and in extracts of the organs ; it is said to be par- 
ticularly rich in the milk. It is present in the 
serum of an artificially produced blister, and it has 
been recommended that blistering be resorted to 
in order to obtain serum for the test. The bile 
often agglutinates the typhoid bacillus, but the 
power has no necessary relationship to a pre-exist- 
ing infection ; it is possible that the agglutination 
in this case is due to obscure chemical causes 



Distribution of 
Agglutinins 
in Body. 



96 



INFECTION AND IMMUNITY 



Inheritance. 



Agglutination 
and Immunity. 



rather than to the usual serum agglutinin. The 
administration of pilocarpin causes a rise in the 
agglutinating power of the tears, sputum and some 
other body fluids; the drug increases cell secre- 
tions. 

When typhoid fever occurs during pregnancy, 
agglutinins may appear in the serum of the fetus. 
On the one hand it has been held that agglutinin 
passes from the mother to the fetus, or, on the 
other hand, that the presence of agglutinins arises 
from infection of the fetus itself. 

Although the milk may be very rich in agglu- 
tinin, it is doubtful if the serum of a breast-fed 
child undergoes much increase in its agglutinating 
power because of the ingestion of the milk. The 
intestinal juices (trypsin) digest agglutinin?. 

The origin of agglutinins in the animal body is 
not known. 

One of the most interesting and important phe- 
nomena in the study of immunity is the so-called 
Pfeiffer reaction. An animal which has been 
rendered immune to cholera by repeated injections 
of cholera vibrios has the power of digesting or dis- 
solving the latter when they are placed in the fresh 
serum or in the peritoneal cavity of the immunized 
animal. Gruber and Durham were studying this 
phenomenon in the test tube when they first ob- 
served the agglutination reaction. It was found 
that the agglutinating property, as well as the bac- 
tericidal power, was the result of immunization. 
Inasmuch as an increase in the bactericidal power 
of a serum points to the existence of an acquired 
immunity, the question naturally arises: Does the 
associated property of agglutination have a similar 
significance ? 



RELATION TO IMMUNITY. 97 

Many observations indicate that the two activi- 
ties are distinct; that they depend on different 
substances in the serum. The following are the 
important points involved : 

1. The bactericidal power is destroyed at 56 C, 
while agglutinins resist a temperature of 62 C. 

2. In certain cases it has been possible to cause 
the bacteria to absorb the agglutinin from the 
serum, leaving the bactericidal substance intact. 

3. A serum may be bactericidal, but not agglu- 
tinating. 

4. During the course of natural or experimental 
typhoid fever or cholera the development of the 
agglutinating and bactericidal powers may not be 
parallel. In cholera, the agglutinating power may 
disappear soon, but the bactericidal power remains 
for a long time. 

5. Micro-organisms which have been killed by a 
bactericidal serum may lose their toxicity; ag- 
glutinated bacteria remain virulent. 

Besredka found an apparent relationship be- 
tween agglutination and immunity; if typhoid 
bacilli were agglutinated before they were injected 
into the abdomen of a guinea-pig the animal would 
recover, but if they were not agglutinated death 
resulted. The explanation offered for this loss of 
virulence is that the bacilli being agglutinated and 
immobilized are more readily taken up by the 
phagocytes; if phagocytosis is inhibited by some 
means the agglutinated organisms are found to be 
still virulent. 

Koch has attempted to use the agglutination 
test with the tubercle bacillus as an index of im- 
munity against tuberculosis. This is not accepted 
as a reliable test for the immunity, but is perhaps 



Technic of the 

Agglutination 

Test. 



The Bacterial 
Suspension. 



98 INFECTION AND IMMUNITY. 

a general index of the ability of the individual to 
form antibodies for this organism. This method 
was devised inasmuch as the bactericidal action of 
a serum on the tubercle bacillus is not readily de- 
termined. 

One may use two methods of determining the 
agglutination of bacteria: 1. The macroscopic or 
naked eye observation of the clumping and sedi- 
mentation of a homogeneous suspension of the 
bacteria in test-tubes; 2, the microscopic observa- 
tion of the clumping of the organisms when the 
latter are mixed with serum and mounted as a 
"hanging-drop" preparation. 2 

When the organism to be tested grows rapidly, 
it is the custom to use a young culture, one which 
has grown on an agar surface or in bouillon for 
from eighteen to twenty-four hours. Older cul- 
tures of the typhoid bacillus or of the cholera 
vibrio are agglutinated with more difficulty than a 
young culture. If an agar culture is used, the 
bacteria may be washed from the surface by pour- 
ing five or ten cubic centimeters of physiologic salt 
solution into the tube and shaking vigorously ; the 
resulting suspension is then ready for use. For 
either the macroscopic or microscopic test it is 
absolutely essential to have a homogeneous suspen- 
sion of the bacteria, in order to avoid misinterpre- 
tations which may be occasioned bv the accidental 



2. For a hnnging-drop preparation it is necessary to have 
a slide with a sancer-shaped depression on one surface. A 
drop of the solution to be examined is mounted on a cover- 
glass, and the latter is then mounted, drop side down, over 
the depression and the edges of the cover-glass sealed with 
vnsolin or paraffin. There is ample room for motile organ- 
isms to swim about in such a preparation, and the loss of 
motility incident to agglutination is readily observed. 



TECHNIC. 99 

or natural clumping of some of the organisms; 
the tubes should be shaken thoroughly before the 
emulsions are used. This uniformity of suspen- 
sion is readily accomplished with such organisms 
as the typhoid bacillus and cholera vibrio, motile 
organisms, but when they grow in chains (strep- 
tococcus) or in coherent masses (diphtheria and 
tubercle bacilli) more violent measures must be 
resorted to. Daily shaking of a liquid culture of 
the diphtheria or tubercle bacillus is fairly effec- 
tive, but the medium must be passed through a 
paper filter before it can be used safely; in this 
way the larger* clumps are removed. Some inves- 
tigators dry a large quantity of tubercle bacilli, 
grind them up thoroughly in an agate mortar and 
suspend the particles in salt solution; the frag- 
mented condition of the organisms does not inter- 
fere with their participation in the reaction. One 
should have a uniform technic in preparing a bac- 
terial emulsion in order to obtain as nearly as pos- 
sible the same number of bacteria in a given vol- 
ume of solution, on different occasions. For exam- 
ple, one may uniformly suspend a twenty-four- 
hour agar culture in ten cubic centimeters of salt 
solution. A uniform technic makes it possible to 
observe the quantitative relationship which exists 
between the mass of bacteria to be agglutinated 
and the agglutinating power of the serum. 

To obtain serum for the test one may resort to To obtain 
blistering; place a cantharides plaster from one- 
half to three-fourths of an inch square on the ab- 
dominal skin, protect it with a dressing, and in 
about twelve hours remove the serum with a steril- 
ized hypodermic syringe. Or, one may collect in a 
small test tube .5 to 1 c.c. of blood from the lobe 

LOFC. 



Serum. 



100 INFECTION AND IMMUNITY. 

of the ear or finger-tip, and draw off the serum 
after it has separated by clotting. It is the cus- 
tom in some well-equipped laboratories to fill sev- 
eral U-shaped capillary tubes with blood from the 
lobe of the ear and to separate the blood from the 
serum at once by centrifugation. The custom of 
drying a few drops of blood on a coverglass or on 
filter paper, and of sending this preparation to a 
laboratory for the agglutination reaction, has been 
practiced quite extensively, and is a justifiable 
procedure when it is not possible to collect the pure 
serum. It has the disadvantage that the experi- 
menter never knows exactly how much blood has 
been collected, and consequently can not perform 
the test with exact dilutions of the serum, the im- 
portance of which will be pointed out below. The 
red corpuscles and debris in such a preparation also 
interfere with the clearness of the field in micro- 
scopic examination, a difficulty which may be 
partly overcome by filtering the dissolved serum. 
m Serum When onlv a small amount of serum is available, 

Dilutions. ... , „ . . , , -. 

it is necessar}' to use the microscopic method. 
Normal human serum, when concentrated, and 
even when diluted to one in ten or higher, some- 
times agglutinates the typhoid bacillus and some 
other organisms; the same serum, when diluted to 
one in forty or one in sixty, may not agglutinate. 
The serum of a typhoid patient, however, or of a 
typhoid convalescent rarely fails to agglutinate in 
these higher dilutions. It is generally held that 
a dilution of one in forty or fifty is sufficiently 
high to eliminate the possibility of agglutination 
by a non-typhoid serum, and sufficiently low to 
render the serums of all, or nearly all, typhoid pa- 
tients agglutinating. The necessity for dilution of 






MEASUREMENTS. . 101 

the serum is emphasized by the additional fact 
that infections with related organisms, as the colon 
bacillus, cause a slight increase in the agglutinat- 
ing power for the typhoid bacillus along with a 
relatively large increase of colon agglutinins. A 
test with a low dilution of this colon serum might 
give a positive reaction with the typhoid bacillus 
and lead to an incorrect interpretation; but 
if a dilution of one in forty were used, the non- 
agglutination of the typhoid bacillus would speak 
against a typhoid infection. This will be consid- 
ered under "group agglutination" (Chapter X). 

A convenient method of measuring small The "Loop" 

- -,, -, , - Measurement. 

amounts or culture and serum is by means of a 
fine platinum wire which is bent at its tip to form 
an eyelet or "loop." 3 If one places one loop of 
serum into a small watch glass or hollow-ground 
slide, and adds nine loops of bouillon or of salt 
solution, a dilution of one in ten is reached. Five 
loops of this mixture with five of the diluent gives 
a dilution of one in twenty. One loop of the sec- 
ond dilution, to which is added one of the culture 
suspension, gives the desired dilution of one in 
forty. The last may be mixed directly on the 
coverglass, and then inverted on a hollow-ground 
slide. It is readily seen how with even a minute 
quantity of serum, one may make the test with di- 
lutions of one in ten, one in twenty, one in thirty. 
one in forty, etc., details which are necessary for 
a correctly performed test. It is important that 
in the different dilution? the same amount of bac- 
terial emulsion be used. 

3. Pfelffer Introduced a conventional "loop" of such 
dimensions that it holds 2 milligrams of bacterial cells as 
they are taken from a solid surface, like that of agar. 



102 



IXFECTIOX AXD I M MUX ITT. 



The Microscopic 
Reaction. 



The Macroscop- 
ic Reaction. 



In the macroscopic test, more serum is neces- 
sary, though the quantity need not be large, and 
the dilutions are made in test tubes of suitable 
size. One should always deal with definite quan- 
tities of the serum dilutions, and should always 
add the same amount of bacterial emulsion in the 
various tubes involved in a test. 

If agglutination occurs in the microscopic prep- 
aration described above, one sees, with the high 
power, in the course of from fifteen minutes to a 
half-hour, that two or more micro-organisms 
which come in contact have a tendency to remain 
in this position. In the case of a motile organism 
(typhoid) the movements may be exaggerated for 
a time. In the course of the next few hours, other 
cells are added to incipient groups and new groups 
originate. Motility becomes less and less and event- 
ually ceases, in a characteristic reaction. The 
maximum change has taken place in from six to 
eight hours. Not less than four or five cells which 
are permanently agglutinated are considered in- 
dicative of a positive reaction; the test is most 
decisive when large masses are formed, so large that 
they are seen readily with a low magnification. A 
similar preparation to which no serum has been 
added should always be made, in order to eliminate 
spontaneous or "auto-agglutination" as a possible 
source of error. 

In a macroscopic test, the uniform cloudiness of 
the mixture of serum and bacteria becomes 
changed by the formation of smaller and larger 
flakes or clumps of bacteria, which in the course of 
a few hours sink to the bottom as a white precipi- 
tate, leaving a clear overlying fluid. Here also a 



UXIT OF AGGLUTIXIX 



103 



control tube, to which no serum has been added, 
should be preserved for comparison. 

The body temperature, which may be obtained 
in a thermostat, facilitates the reaction. 

The value of an agglutinating serum can not be The Agglutinin 
expressed in units with the exactness that is at- 
tained in measuring diphtheria antitoxin for the 
following reasons : 1, The limits of the reaction are 
not sufficiently definite ; 2, a given mass of bacteria 
has the power of absorbing varying amounts of 
the agglutinating substance, depending on the con- 
centration of the latter; and 3, it is impossible to 
obtain standard bacterial emulsions. 

One may arbitrarily decide on a unit similar to 
that of Ziipnik, in which a serum which is able 
to agglutinate a given mass of bacteria in a dilu- 
tion of one in forty is taken as the standard. If a 
similar amount of a serum agglutinates in a di- 
lution of 1 in 120 it is said to be of threefold 
strength. 

The value of the agglutination reaction as a 
clinical diagnostic aid Avill be considered later in 
connection with the individual diseases. 

A consideration of agglutination would be in- Agglutination 
complete if one did not mention the phenomenon cinSsdes. 11 
as it occurs with cells other than those of bacteria, 
in particular the red blood cells. The serums of 
many animals, as stated in a previous chapter, are 
toxic for the erythrocytes of some other species. 
Tn some instances, the corpuscles lose their hemo- 
globin under the influence of the serum (hemoly- 
>i>): in other instances, or even with the same 
.-enims. the corpuscles are thrown into clumps and 
settle to the bottom of the test tube, leaving a clear 
overlying fluid. The analogy with the bacterial 



104 INFECTION AND IMMUNITY. 

agglutinins goes still further, in view of the fact 
that the formation of these '^hemagglutinins" 
may be induced artificially in the body of an ani- 
mal by the injection of erythrocytes from another 
species. An animal does not form agglutinins for 
its own cells (auto-agglutinins), and rarely, if 
ever, for the cells of another member of the same 
species (iso-agglutinins). What is said in the 
next chapter concerning the specificity of the bac- 
terial agglutinins also holds for the hemaggluti- 
nins. 
Plant Hemag- Certain plant toxins, true toxins with hapto- 
phorous and toxophorous structures, agglutinate 
red blood cells: ricin, abrin, crotin, etc. Some of 
the earliest and most important work which 
Ehrlich has done in the field of immunity was ac- 
complished with these plant toxins. 



glutinins. 



CHAPTER X. 



THE NATURE OF THE SUBSTANCES CONCERNED IN 
AGGLUTINATION. 

Two substances are concerned in agglutination: Terms. 
one, the active or agglutinating substance, exists 
in the serum, while the other, the substance acted 
on or the agglutinable substance, is present in the 
bacteria. The agglutinable substance is generally 
supposed to be passive in the reaction, while the 
agglutinating property seems to possess a ferment- 
like element, which acts on the agglutinable sub- 
stance. Agglutinin, the term used in the preced- 
ing chapter, is now generally applied to the sub- 
stance in the serum. Recently the bacterial con- 
stituent has been called agglutinogen, because of 
the belief that the agglutinable substance, when 
introduced into the animal body, stimulates the 
latter to the formation of agglutinin; hence ag- 
gutinogen means, not agglutination-producing, 
but agglutinin -producing. These shorter terms 
will be used for the sake of convenience. 

The presence of agglutinogen in an organism Agglutinogen. 
may be demonstrated in three ways: 1. The mere 
fact of its agglutin ability by a serum is evidence 
of the presence of an agglutinable substance. 2. 
If during infection or immunization the serum ac- 
quires agglutinating properties, the bacterium pos- 
sesses an agglutinogen^ substance. 3. If a cul- 
ture is mixed with a serum containing the specific 
agglutinin, and after a period of contact is re- 
moved by centrifugation, the resultant disappear- 



106 INFECTION AND IMMUNITY. 

ance of agglutinin from the serum, which may be 
demonstrated, shows that something in the bac- 
teria (agglutinogen) has combined with the ag- 
glutinin. 

Distribution of The location of agglutinogen in the bacterial 
cells has received some discussion. There is a tend- 
ency to believe that it exists in the cell envelope or 
perhaps on its surface. It appears to be formed in 
the cell, and, in some cases, it may be excreted into 
a surrounding medium; certainly when bacteria 
die and disintegrate agglutinogen is liberated. The 
filtrates of certain cultures (entirely free from 
bacterial cells), when injected into animals, will 
cause the formation of agglutinins. Also, just as 
a micro-organism is able to absorb agglutinin from 
the corresponding antiserum by a process of 
chemical union, so a nitrate of the type mentioned 
is able to neutralize the agglutinating power of the 
serum. In these instances agglutinogen becomes 
free as a consequence of disintegration of some of 
the bacterial cells. 

The Precipjta- The filtrates of certain cultures exhibit another 
phenomenon when they are mixed with their spe- 
cific antiserums; this has to do with the bacterial 
precipitins of Kraus. If, for example, the filtrate 
of an old typhoid bouillon culture is mixed with 
antityphoid serum, a distinct precipitate is formed 
which eventually settles to the bottom of the tube. 
This is a specific reaction, and does not occur if the 
nitrate is mixed with some other immune serum. 
It is thought by some that this so-called preci pi- 
table substance in the filtrate is identical with the 
agglutinable substance (agglutinogen), but this 
point is still the subject of investigation. 

Agglutinogen may be extracted from micro- 



AGGLUTINOGEN AND AGGLUTININ 



107 



organisms by chemical processes. The presence 
of the substance in the extracts becomes manifest 
when immunization with them causes the forma- 
tion of an agglutinating serum. This, again, is 
the "test of immunization/" 

The agglutinogen of one bacterium is not iden- Multiplicity of 

"|* *r . Agglutinogens. 

tical with that of any other. If they were identi- 
cal, immunization with the one would yield an ag- 
glutinating serum of equal power for both cells: 
this, however, is not the result obtained. On the 
other hand, the agglutinins of two different organ- 
isms may coincide to a certain degree, as will be 
shown under the subject of "group agglutination.** 
Certain experiments go to show that the agglutin- 
ogen of even a single micro-organism is not uni- 
form substance. One portion is heat-susceptible, 
being destroyed at 62 C. while another portion is 
said to resist a temperature of 165 C. Such tech- 
nical questions continue to be investigated. 

Agglutinogens are said to pass through semi- 
permeable membranes, while agglutinins do not. 

Smith and Eeagh distinguish two kinds of ag- Flagellar 
glutinogen in those bacteria which possess flagellar. Agglutinogens, 
one peculiar to the cell body, and the other to the 
flagellar. 

Agglutinin may be precipitated completely from A >ro fu t 7 n i ^ s of 
a serum by the sulphates of magnesium or ammo- 
nium, when the salts are used in proper concentra- 
tions. Because of their reaction to such precipi- 
tating agent-, agglutinins are thought to belong to 
the globulin fraction of serums ; whether globulins 
or not, they are precipitated with them. 

Agglutinins resist digestion with pepsin and 
papayotin, but are destroyed after prolonged ex- 
posure to the action of trypsin. An agglutinating 



108 INFECTION AND IMMUNITY. 

serum which is dried and kept free from moisture 
and the action of light retains its power unaltered. 
Similar to agglutinogen, agglutinin is thought not 
to be a uniform substance, one portion being sus- 
ceptible to heat, and another portion resistant; 
these have been called alpha and beta agglutinins. 

structure of It is convenient to speak of the reaction between 
agglutinin and agglutinogen, and of the process in 
the body through which agglutinins are formed, in 
terms of the side-chain theory. Accordingly, if 
that constituent of micro-organisms which we have 
termed agglutinogen is the substance which stimu- 
lates the tissues to form agglutinin, we must as- 
sign to it a haptophorous group through which it 
may unite with the receptors of the tissue cells. 
This haptophore comes into play again in the union 
between agglutinogen and agglutinin, which pre- 
cedes agglutination. There is no reason for as- 
signing to agglutinogen any other structure than 
this single haptophore; it is a passive body, similar 
to antitoxin, and has no other function than that 
of uniting either with cell or with agglutinin. 

structure of Agglutinin also must have a haptophorous or 

Agglutinin. ,. ... . , ., \ l ,. 

binding group, inasmuch as it enters into combina- 
tion with agglutinogen. In addition to this bind- 
ing group, experiments have shown that agglutinin 
possesses a toxic constituent, which is analogous 
to the toxophorous group of the toxin molecule. 
In this case, however, it is called a zymotoxic, 
Zymotoxic z y mo ph° ro ' as .or agglutinophorous group ; suppos- 
Group. edly it has a ferment-like activity (Fig. 6). The 
analogy with toxins goes further, in that the 
zymotoxic group of agglutinin may degenerate or 
may be destroyed, leaving the haptophorous group 
with its binding power for agglutinogen practi- 



AGGLUTINOIDS. 



109 






cally unaltered; these are agglutinoids, just as Aggiotinoids. 
toxins when changed in a similar way are called 
toxoids. A serum which is rich in agglutinin may 
be changed into one rich in agglutinoid by expo- 
sure to a temperature of from 60 to 75 C, and by 
the action of acids or alkalies; the change also 
takes place spontaneously in the course of time, 
when the agglutinin is in solution. 

Agglutinoids are detected by methods analogous 
to those used in the recognition of toxoids. If 
toxoids unite with all the antitoxin in a solution, 
there naturally remains no antitoxin to unite with 
true toxin which may be added subsequently. Sim- 
ilarly, if all the agglutinogen in a mass of micro- 
organisms has united with inactive agglutinoid, 
agglutinin which is added subsequently would have 
no point of attack and the reaction of agglutina- 
tion would not occur. So we may say that when 
bacteria are treated with a serum which has lost 
its original agglutinating power, and the bacteria 
are thereby made insusceptible to the action of a 
fresh agglutinating serum, the former serum con- 
tains agglutinoids. 

Sometimes it is found that even a fresh serum, 
when concentrated, will cause less agglutination 
than when diluted. This has been referred to the 
presence of agglutinoids which have a stronger 
affinity for agglutinogen than has the agglutinin; 
when of this character they are called proagglu- 
tinoids, and accordingly are analogous to the pro- 
toxoids mentioned earlier. As the serum is diluted 
the concentration of the proagglutinoids becomes 
less, arid at a time when they are so dilute that they 
have no influence on the reaction, the agglutinins 



Proagglu- 
tinoids. 



110 INFECTION AND IMMUNITY. 

are still present in such quantity that agglutina- 
tion is brought about. 
Two stages in The presence of some salt is necessary for the 
Agglutination. occurrence f agglutination. Bordet found that 
if the salts were removed from the serum and from 
the suspension of bacteria by dialysis, and the two 
were then mixed, agglutination did not occur; if 
a small trace of sodium chlorid was added the re- 
action took place promptly. Furthermore, if the 
serum was completely removed from the bacteria 
by repeatedly washing them in distilled water, it 
was found that the microbes had absorbed the ag- 
glutinin, but the latter remained inactive until the 
salt was added. 

This experiment not only suggests a haptophor- 
ous as distinguished from a zymotoxic group, but 
also indicates that agglutination consists of two 
phases. The first phase represents the union of 
agglutinin with the bacteria, while in the second 
are included the other changes necessary for the 
clumping of the organisms, in which the activity 
of the zymotoxic group is represented. The action 
of the salt, just cited, is unknown. 

The properties of serums which are of interest 
in immunity are now being studied by chemists, 
notably by Arrhenius. The study of mass action, 
of chemical equilibrium between agglutinin and 
agglutinogen, for example, and of the dissociation 
of the compound after it has once formed, are 
subjects under investigation, but which are too 
technical to be entered on here. 
Group "Group agglutination" has been referred to. By 
gg utmation. ^. g ^ g mean t foe ability of an antimicrobic serum 
to agglutinate certain other organisms which mor- 
phologically, biologically and often pathogeneti- 



GROUP AGGLUTIXATIOX. Ill 

cally, are closely related to the homologous bac- 
terium. In these instances, the agglutinating 
power is greatest for the homologous organism, 
and the degree to which the heterologous organisms 
are agglutinated is, to some extent, an index of 
the proximity of the relationship of the latter to 
the former. Antityphoid serum has been found to 
agglutinate the psittacosis, colon, paracolon, and 
paratyphoid bacilli and Bacillus enteritidis. but 
the action is never so strong as on the typhoid 
bacillus itself. We are to understand that this 
power to agglutinate related organisms represents 
something more than the normal property of the 
serum; there has been an actual increase in agglu- 
tinin for the heterologous bacteria as a result of 
infection or immunization by the primary organ- 
ism. 

Having typhoid fever in mind, this is a rule 
which works both ways. Infections with the colon 
bacillus and related organisms, and sometimes 
with organisms not closely related, as the staphylo- 
coccus, may cause an increase in agglutinin for the 
typhoid bacillus. The importance of this fact is 
evident, and it may explain the positive Gruber- 
Widal reaction sometimes found in infections 
other than typhoid. 

Inasmuch as the highest agglutinating power is chief Agglutinin 
always manifest against the homologous organism. fjnh,s? ag9,u 
this is spoken of as the chief agglutinin (Tlaupt- 
agglutinin) of the serum, while the weaker agglu- 
tinins for other organisms are called partial or ad- 
ventitious agglutinins, or coagglutinins (Mitag- 
glutinin ) . 

The phenomenon of group agglutination would Specificity, 
seem to violate the specificity which we are in the 



112 INFECTION AND IMMUNITY. 

habit of attributing to the reactions of immunity; 
yet a reasonable explanation has been offered for 
the occurrence. It is probable that the proto- 
plasms of all cells have certain constituents in 
common, and that the closer the relationship be- 
tween two different cells the greater is the simi- 
larity of their constituents. In view of this prob- 
ability, Durham has used the following illustra- 
tion in the explanation of group agglutinations : 
The typhoid bacillus contains certain constituents, 
agglutinogenic molecules, which one may desig- 
nate as a, b, c, d, and e ; these differ among them- 
selves in unknown respects, but each is able to 
stimulate to the formation of a corresponding ag- 
glutinin. The serum, then, would have the ag- 
glutinin molecules A, B, C, D and E, also differing 
among themselves, but having at least one property 
in common — that of causing agglutination of the 
typhoid bacillus by uniting with the correspond- 
ing agglutinogenic molecules. In this sense noth- 
ing could be more specific. The Bacillus enteri- 
tidis, closely related to the typhoid organism, may 
possess the agglutinogenic molecules c, d, e, f, g, 
and h, and following the principle expressed above 
would stimulate, in the body, to the formation of 
the agglutinin molecules C, D, E, F, Gr and H. 
Inasmuch as the agglutinogens c, d and e are com- 
mon to the two bacilli, the agglutinins C, D and E, 
which are present in both serums, would affect 
either of the two organisms. The typhoid serum, 
however, would contain five agglutinins for the 
typhoid bacillus and only three for the Bacillus 
enteritidis, consequently the action would be 
stronger against the typhoid bacillus; mutato mu- 
tandis, the same applies to the enteritidis serum. 



SERUM DILUTIONS. 



113 



The same line of reasoning would explain the in- 
creased agglutinating power of an anticolon serum 
for the typhoid bacillus. 

A further elaboration of this principle may be 
made in a case in which two different strains of 
the same organism (typhoid bacillus) have some- 
what different agglutinogenic molecules; conse- 
quently the homologous immune serums for the 
two organisms might not coincide in their ag- 
glutinating powers for a third strain of the bacil- 
lus. 

In view of the points mentioned, it is clear that importance 
specificity of a given serum may be determined Dilutions. 
only by diluting the serum to such an extent that 
the coagglutinins practically are eliminated, the 
chief agglutinin being present in so much greater 
concentration that it is still able to agglutinate 
the homologous bacterium. 

Theoretically, it is also important for the spe- 
cificity of the reaction that the particular strain 
of the organism to be used for the test correspond 
in its agglutinogenic molecules or receptors with 
those of the strain used for the immunization ; the 
agglutinogenic receptors should be typical for the 
organism. 

It is doubtful if group agglutination occurs 
among all closely related bacteria, inasmuch as 
Kolle found that it did not exist among the vib- 
rios. 

It is thought possible that the multiple agglu- Mixed. 
tinating power of a serum may be caused by mixed ,nfect,ons - 
infections in some instances. Although this is to 
be kept in mind, one should not overestimate its 
diagnostic importance, because a similar multi- 



114 INFECTION AND IMMUNITY. 

plicity may result from infection by a single micro- 
organism. 

production of The explanation of the production of aggluti- 
Aaa,U Ehr!?ch n i ns by "the body, according to the conception of 
Theory. Ehriuj]^ is similar to that already given for the 
production of antitoxins. That is to say, the ag- 
glutinin molecules are cast-off cell receptors, the 
overproduction of which has occurred as a result of 
their union with the agglutinogenic molecules of 
the bacteria. The antitoxin receptors were rela- 
tively simple, having no other demonstrable struc- 
ture than that of the haptophorous groups through 
which they unite with the corresponding toxin. 

Receptors of We have recognized in the agglutinin receptor two 

Second Order. , ** - -? & . r 

groups, a haptophorous and a zymotoxic; conse- 
quently it must have this same structure when it 
is still a part of the cell. Ehrlich designates it as 
a receptor of the second order, which, being de- 
fined, is a receptor in which a haptophorous and a 
zymotoxic group exist as integral parts of the 
molecule (Fig. 6). 

In accordance with the side-chain theory, the 
ability of an animal to form agglutinins for a cer- 
tain organism would depend on its possession of re- 
ceptors of the second order which are able to unite 
with the agglutinogenic receptors of the bacterium. 
It is well established that different animals may 
not form serums with equal agglutinating powers 
for an organism. The following is a concrete ex- 
ample: Wassermann immunized rabbits, guinea- 
pigs and pigeons with a strain of the colon bacil- 
lus, and tested the three serums with fifteen other 
strains of the same organism. The serum of the 
guinea-pigs readily agglutinated the strain which 
was used for immunization, but scarcely affected 



IN A GGLU1 IX ABILITY. 



115 






the others. The serums of the rabbits and pigeons 
also agglutinated the homologous culture, but the 
coagglutinins which they possessed did not affect 
other strains equally. Consequently, it was sup- 
posed that the cells of the three animals contained 
a limited number of receptors in common, whereas 




Fig. 6. — Graphic representation of receptors of the second 
order and of some substance uniting with one of them, c, 
cell receptor of the second order ; d, toxophore or zymophorous 
group of the receptor ; e, haptophore of the receptor ; f, food 
substance or product of bacterial disintegration uniting with 
the haptophore of the cell receptor. From Ehrlich's 
"Schlussbetrachtungen," Nothnagel's System of Medicine, 
vol. viii. 

other receptors which were present in one of the 
animals were largely wanting in the other two. 

Inagglutinability was mentioned as a charac- 
teristic of certain bacteria, especially the bacillus 
of Friedlander. This condition is much more im- 
portant when it involves an organism which 



Inagglutinabil- 
ity of Some 
Organisms. 



116 INFECTION AXD IMMUNITY. 

usually is agglutinated with ease. In some in- 
stances, the typhoid bacillus when freshly culti- 
vated from a patient, or, indeed, from contami- 
nated water, has been found to resist agglutination 
by a strong serum; the same organism after a 
period of existence on artificial media becomes ag- 
glutinable. Widal and Sicard noted that often the 
serum of a typhoid patient would not agglutinate 
the bacillus which had been cultivated from the 
patient's own body, although the same serum 
would agglutinate laboratory cultures. Cultiva- 
tion of the typhoid bacillus at 42 C. will cause it 
to lose its agglutinable property, but it may be re- 
established by subsequent cultivation at lower 
temperatures. It seems that this variation must 
be due to some change in the bacteria, i. e., in the 
agglutinable substance. It is possible that the 
organism, during its existence in the animal, be- 
comes immunized against the action of the agglu- 
tinin just as the animal becomes immunized 
against the toxic action of bacteria. This condi- 
tion in the micro-organisms would then be repre- 
sented by a great excess of agglutinogenic recep- 
tors, so that a much greater amount of agglutinin 
would be required to cause clumping. It is read- 
ily seen how the use of an inagglutinable strain of 
the typhoid bacillus would affect serum diagnosis. 
Theories of We are to consider that in the phenomenon of 
agglutination a reaction of a chemical or physico- 
chemical nature takes place between the agglutinin 
of the serum and the agglutinogen of the micro- 
organisms, the actual clumping following as a 
consequence of this reaction. It is not a "vital" 
reaction, for dead bacteria may be agglutinated. 



Agglutination. 



THEORIES OF AGGLUTINATION. 117 

" Theories of agglutination have to do, not with 
the existence of agglutinin and agglutinogen, but 
rather with the nature of the reaction between the 
two, and the influences which bring about the 
clumping after the reaction has occurred. The 
original theory of Gruber supposed that the serum 
so affected the bacteria that they became sticky; 
consequently, as they came in contact, they were, 
so to say, glued together. Dineur thought changes 
occurred in the flagellar of the organisms, a theory 
which is untenable because some bacteria are ag- 
giutinable which do not possess flagellar Em- 
merich and Loew refer agglutination to the action 
of an enzyme which is produced by the bacterium 
itself, a theory which is not given general credence. 
Bordet excludes the vitality or motility of the or- 
ganisms as factors, and believes that the process is 
purely a physical one, because of the fact that 
some known chemical substances may be made to 
precipitate or to agglutinate certain other sub- 
stances (precipitation of colloids by salts) ; the 
theory presupposes some change in the molecular 
attraction between the microbes and the. surround- 
ing fluid. 

Other theories have to do with the question of 
precipitation. As previously stated, when the fil- 
trates of cultures of certain organisms are mixed 
with their corresponding immune serums, precipi- 
tates occur in the mixtures. It was mentioned 
that the substance in the filtrate which takes part 
in the precipitation may represent, in part, the ag- 
jrhi tin able substance which has been excreted by 
the bacteria. Nicolle supposes that the agglutin- 
able substance resides in the external layer of the 
bacteria and that when llio scrum is added a coag- 



118 INFECTION AND IMMUNITY. 

ulation occurs in the envelope, rendering coales- 
cence with the envelopes of other individuals pos- 
sible. The theory of Paltauf that the agglutinable 
substance finds its way to the surface of the bac- 
terium and is precipitated by its union with ag- 
glutinin is somewhat similar. The shell of the co- 
agulated substance accounts for the sticky charac- 
ter which the envelope acquires, according to the 
theory of Gruber. Paltauf cites observations 
which tend to show, that some substance actually 
is extruded from the micro-organisms during ag- 
glutination, and that in properly stained speci- 
mens it can be seen as a precipitate surrounding 
and between adjacent organisms. 

The multiplicity of theories leads one to suspect 
that the true nature of the process remains obscure. 



CHAPTER XI. 



PRECIPITINS. 

Because of their scientific importance and cer- 
tain practical features, the serum-precipitins 
should receive something more than the incidental 
mention which has been given them under agglu- 
tination and in other chapters. 

In 1897 Kraus discovered that bouillon cultures Bacterial 
of the organisms of typhoid, cholera and plague, Prec,prt,ns - 
from which the bacteria had been removed by fil- 
tration, would cause precipitates when mixed with 
their respective antiserums. The reaction is spe- 
cific. As stated later, however, this specificity 
holds only when those quantitative relationships 
are observed which were found so essential for the 
agglutination test. The precipitins of Kraus are 
the bacterial precipitins. He proposed their use 
for the identification of micro-organisms. If, for 
example, one has in hand a culture which he sus- 
pects to be that of the typhoid bacillus, it may be 
grown in a liquid medium, the cells removed by 
filtration, and the filtrate mixed with a known 
antityphoid serum; if a precipitate occurs when 
the serum is sufficiently diluted, the reaction indi- 
cates that the organism in question is the typhoid 
bacillus. Inasmuch as precipitins are formed dur- 
ing the course of some infections it may be possible 
to use them in clinical diagnosis, but for either 
bacterial or clinical diagnosis the agglutination 
tost is more readily performed and interpreted. 



120 



INFECTION AND IMMUNITY. 



Lactoserum. 



Phytoprecipi- Pliytoprecipitins are produced by immuniza- 
oprecipitins. tion with albuminous substances of plant origin, 
as ricin and albumin from grains, and their action 
is specific for the homologous substance. 

Zooprecipitins are obtained by immunizing with 
animal albumins. Through the work of Wasser- 
mann and Uhlenhuth, of Nuttall, and others, it 
has been demonstrated as a general law that im- 
munization with an albumin from whatsoever 
source gives rise to the formation of a precipitin 
which manifests its action only against the par- 
ticular albumin used for the immunization. Hence, 
the albumin of a particular serum, in some un- 
known respect, is different from that of all others ; 
it is special to the species. 

Immunization with milk causes the formation 
of a precipitin which throws down the casein of 
the milk used for injection, but not that of milk 
from another species. The milk of the goat may 
be differentiated from that of the cow by the use 
of the lactoserum. 

Likewise, after the injection of egg-albumin a 
precipitin is formed which is specific for the type 
injected. 

Three substances are open to study in the pre- 
cipitation reaction. First, the fluid or substance 
which is used for immunization ; it bears the name 
of precipitogen, i. e., the precipitin-producing sub- 
stance, Second, the specific constituent of the 
precipitating serum, i. e., the precipitin. Third, 
the precipitate, which is a consequence of the reac- 
tion between precipitogen and precipitin. We are 
able to recognize in this instance the actual end- 
product of a reaction, a condition which is not so 
oasilv realized in other "immunity reactions." Tt 



Precipitogen, 

Precipitin and 

Precipitate. 



PRECIPITIN 



121 



is true, of course, that little has been learned con- 
cerning the nature of the end-product ; its chemis- 
try is as dark as that of the proteids in general. 

As stated in the chapter on "Natural Immun- 
ity.' 7 normal serums occasionally have the power 
to cause precipitates in other serums. Precipitins 
for egg albumin and goat serum have been found 
in extracts of organs, although at the same time 
they were absent from the serum of the animal. 
In this case the active bodies exist in the cells as 
"sessile receptors." and by the process of extraction 
they are brought into solution. During immuniza- 
tion these same receptors are stimulated to over- 
production and are thrown into the circulation as 
free precipitin receptors. 

The power of forming precipitins may be widely 
distributed among the organs. This function lias 
been assigned to the leucocytes (Kraus and Leva- 
diti. Moll), and in one case they were formed 
locally in the anterior chamber of the eye (v. 
Dungern. Romer). 

For the artificial production of precipitins the 
precipitinogenous fluid may be injected into the 
veins, peritoneal cavity or the subcutaneous tissue. 
Within from four and a half to five days the pre- 
cipitin has been formed to such an extent that it 
may be demonstrated in the serum of the im- 
munized animal. 

As in the case of agglutinin formation, not all 
animals have equally the power of forming a pre- 
cipitin for a given albumin. This point, as re- 
lated to serum precipitins, is of particular impor- 
tance, and involves a factor which is of no conse- 
quence in bacterial agglutinins. In the first 
place, an animal will not form a precipitin which 



Formation of 
Precipitin. 



Concerning 
Autoprecipi- 
tins and Iso- 
precipitins. 



122 INFECTION AND IMMUNITY. 

is active against its own serum, i. e., by bleeding 
an animal and reinjecting the serum a specific pre- 
cipitin is not formed. If formed it would be an 
autoprecipitin, and, as a rule, animals do not form 
antibodies for their own tissue constituents. 
Again, animals are unlikely to form antibodies for 
the tissue constituents of other members of the 
same species; these, when formed, are called iso- 
bodies. Schiitze immunized thirty-two rabbits 
with serum from the rabbit and obtained an iso- 
precipitin from only two of the number. In the 
third place, animals do not readily form anti- 
bodies for the tissue constituents of other animals 
which zoologically or biologically are closely re- 
lated. Immunization of the guinea-pig with the 
serum of the rabbit, a pigeon with that of a 
chicken, or a monkey with human serum, are pro- 
cedures which usually do not yield precipitating 
serums. 
Nature of Chemically, little is known of precipitins. They 
Precipitins. are thrown down by ammonium sulphate in con- 
junction with the euglobulin fraction of serum, and 
are destroyed by those substances which alter al- 
buminous bodies, as acids, alkalies, pepsin and 
trypsin. 
Specific When serum is heated to from 50° to 60° C. its 
ability to cause a precipitate in the homologous 
precipitogen is destroyed, although it may be dem- 
onstrated that the power to combine with the lat- 
ter is unchanged. Hence precipitin, like agglu- 
tinin, is composed of two groups, a binding or 
haptophorous, and a ferment-like group in which 
the active property reside ; the latter is the coaa-- 
ulin of the molecule. When precipitin has lost its 
coaguliu it becomes precipitoid. and as precipitoid 



Inhibition. 



SPECIFIC IXHIBITIOX 



123 



it may unite -with precipitogen and thereby inhibit 
the action of a fresh precipitin which may be 
added later. When a precipitating serum has 
partly degenerated into precipitoids, that is. when 
it consists of a mixture of precipitin and precipi- 
toid. it is found that the latter have the greater 
affinity for precipitogen; hence, in concentrated 
solutions of the serum, precipitoid may be present 
in sufficient quantity to bind all the available pre- 
cipitogen. and the reaction would not occur in 
spite of the presence of active precipitin. This is 
spoken of as specific inhibition. The action is 
analogous to that of toxoids and agglutinoids, and 
the phenomenon is mentioned again in this in- 
stance in order to emphasize the fact that certain 
principles of action are common to many of the 
immune substances. Precipitoids. like toxoids and 
agglutinoids. are formed by long standing, by the 
action of heat and light and by other injurious in- 
fluences. 

The molecule of precipitin, like that of agglu- 
tinin, is a receptor of the second order (Fig. 6). 

The attempt has been made to produce antipre- Antipredpitins. 
cipitins by immunization with precipitating 
serums: this is immunization with an immune 
serum. It is reported that antibodies have been 
obtained for lactoserum. but not for bacterial pre- 
cipitins. There is a limit to the cycle of antibody 
formation. 

Precipitogen may be defined as any albuminous 
substance immunization with which will cause the 
formation of a specific precipitating serum. Tn 
addition to those mentioned above, albuminous 
urine, pleural exudates, ascitic fluid and that from 
hydrocele are precipitogens. The same is true of 



Nature of 
Precipftogen. 



124 INFECTION AND IMMUNITY. 

some albuminous fractions of serums, as globulin, 
the precipitating serum for which may be called 
antiglobulin. Kraus believes that the precipitogen 
of bacterial filtrates is associated with albuminous 
molecules. Jacoby obtained by tryptic digestion 
of ricin, a precipitogen which gives no albumin 
reaction. On the other hand, certain precipito- 
gens are destroyed by pepsin and trypsin, a fact 
which indicates their albuminous nature. 

Certain precipitogens are said to consist of a 
thermolabile and a thermostabile portion, the dif- 
ferentiation of which we need hardly consider. 
Precipitoid It is of no little interest that precipitogen, simi- 

Derived from -, , ■ ... • , » , " ,-■ i 

Precipitogen. lar to precipitin, consists of two groups, through 
one of which it unites with precipitin, whereas the 
other has a coagulating function. Egg albumin, 
for example, when heated to rather high tempera- 
tures, loses its ability to participate in the pre- 
cipitation reaction, although it retains its binding 
power for precipitin. In view of the fact that the 
two substances which enter into the reaction have 
similar structures, it is difficult to say which as- 
sumes the passive and which the active role. De- 
generated precipitogen is also called precipitoid. 
In order to distinguish the two precipitoids one 
must speak of the precipitoid of precipitogen. and 
the precipitoid of precipitin. The precipitoid of 
precipitogen yields precipitin by immunization; 
hence, it is all the more analogous to the toxoids. 
Precipitate. The precipitate which is caused when a bacterial 
nitrate is mixed with its specific antiserum forms 
in from one-half hour-to several hours, and appears 
as a coherent white sediment which in the course 
of twenty-four hours has left the overlying fluid 
quite clear. The action of the precipitins for 



FORENSIC TESTS. 



125 



serums is more rapid, and in either case sedimen- 
tation is hastened by placing the fluids at body 
temperature. As intimated above, the occurrence 
of the reaction depends on an intact condition of 
the coagulin groups of both substances. A low 
concentration of organic acid favors, whereas min- 
eral acids and alkalies inhibit or prevent precipi- 
tation ; a neutral reaction is indifferent. The pre- 
cipitate contains albumin, which, however, has be- 
come so changed that it is not susceptible to the 
action of trypsin. The two in combining have in 
some way shut off the point of attack for trypsin. 
A lactoserum precipitates the casein of the corre- 
sponding milk. The presence of salts is necessary 
for the reaction of precipitation. 

Group precipitation is not so pronounced as 
group agglutination, yet it exists to a certain de- 
gree and is of the utmost practical importance in 
attempting to differentiate serums by the precipi- 
tation method. Although bacterial precipitins are 
highly specific, it is important to observe the prin- 
ciple of serum dilution which was emphasized 
under agglutination, in order to obtain the adven- 
titious precipitins in such small amounts that 
they do not interfere with the chief precipitin. 

That feature of the precipitation reaction which 
has the most practical bearing has to do with its 
medicolegal use in the detection of human blood. 
For this purpose it has supplanted the specific 
hemolytic serums, which are to be referred to later. 
Tn the course of investigations it was found that 
even the smallest dried blood stain, although 
months old, would cause the formation of a sedi- 
ment when mixed with its homologous precipitat- 
ing serum. Tt remained for certain important de- 



Group Precipi- 
tation and 
Specificity. 



Forensic Use 
of Precipitins. 



126 INFECTION AND IMMUNITY 

tails to be worked out in order to render the test 
sufficiently reliable for forensic work. The spe- 
cificity of the reaction appeared to be threatened 
somewhat when it was learned that the serum of 
monkeys undergoes precipitation when treated by 
an immune serum which is specific for human 
serum. This is, again, group precipitation. Ad- 
ventitious precipitation is, in fact, so widespread 
that some have felt justified in speaking of a mam- 
malian serum reaction. Hence, in order to insure 
specificity, it has become necessary to use precise 
quantitative methods in differentiating bloods or 
serums by this method. The immune serum which 
is used in the test must be diluted to some extent 
in order to eliminate accidental precipitins; but 
even a more important precaution is the volumet- 
ric measurement of the precipitate which is 
formed. The technic of Schur may be cited. Test 
tubes are so made that the lowermost portion con- 
sists of a graduated capillary tube. One c.c. of the 
fluid to be tested is placed in one of these tubes, to 
which is then added 0.2 c.c. of the precipitating 
serum. The mixture is kept at body temperature 
until the reaction is complete, and the sediment is 
then thrown into the capillary portion of the tube 
by centrifugation for a stated period of time 
(twenty minutes). The volume of the sediment 
may be read by the scale. Nuttall allows the sedi- 
mentation to occur naturally, with the tubes in an 
upright position. Other serums naturally must 
be used as controls. If the "unknown" blood is 
suspected of being human, a control tube must be 
prepared in which a similar amount of known hu- 
man serum is submitted to the same test. If the 
two tubes yield similar amounts of precipitate 



RECOGNITION OF MEATS. 127 

when they are treated with 0.2 c.c. of a precipi- 
tin which is specific for human serum, the identity 
of the "unknown" blood as that of man is estab- 
lished. To obtain the specific precipitin it is cus- 
tomary to immunize rabbits with human serum for 
several weeks. 

Another practical feature of the precipitation identification 

of Meats 

test has to do with the differentiation of meats. A 
precipitogenous substance which is characteristic 
for the animal may be extracted or pressed from 
the flesh, and will yield a precipitate when it is 
mixed with a precipitin of homologous nature. 
This is of particular interest in those countries in 
which the meat of the horse is put on the market 
as a substitute for that of beef. 

The possible relationship of precipitation to bac- 
terial agglutination was referred to in the chapter 
on agglutination. 

In view of the fact that the protoplasm of the Colloids and 
body and the albuminous constituents of serum of immunity! 
have a close relationship to, or really are, colloids, 
investigators have studied certain reactions which 
occur among the known colloids with the expecta- 
tion that the reactions of protoplasm and those of 
serums would receive some elucidation. Not much 
advancement can be made, however, until the prop- 
erties of colloids are more thoroughly understood. 

Substances which go into solution were classi- 
fied by the English physicist, Graham, as crystal- 
loids and colloids. Crystalloids include many in- 
organic salts. Usually they form clear solutions 
in water and exert osmotic pressure, supposedly 
because of the small size of their molecules. They 
diffuse with some rapidity and many are conduc- 
tors of electricity. Organic colloids comprise such 



128 INFECTION AND IMMUNITY. 

Properties of substances as albumin, starch, dextrin, tannin, 
gelatin and many gums. By proper treatment of 
certain metals and their salts, inorganic colloids 
may be prepared ; for example, ferric hydroxid and 
the sulphids of antimony and arsenic. When col- 
loids are dissolved in water the solutions are often 
more or less opaque, and are sometimes opalescent 
because the particles or molecules are of such size 
that they polarize light. They exist in water either 
as a solution of molecules of great size or as a sus- 
pension of considerable particles or aggregates of 
molecules. In some instances the particles are so 
large that they may be seen by a magnification of 
1,000 diameters, while in others no degree of mag- 
nification renders them visible with the ordinary 
microscope. By the use of the recently devised 
ultramicroscope, however, the finest particles in 
some colloidal solutions may be discerned. Col- 
loidal substances, such as albumin, diffuse very 
slowly and exert little or no osmotic pressure, sup- 
posedly because of the large size of the particles. 
The} 7- do not conduct electricity, but the particles 
themselves react to the electric current by altera- 
tions in the direction of their motion (i. e., toward 
the positive or the negative pole), and, moreover, 
carry electric charges themselves. 
Precipitation The features of colloids which bring them into 
°Eiectroiytes V . relation with the subject in hand are their coagu- 
lable nature in certain instances and the fact that 
their particles may be agglutinated or precipi- 
tated by the addition of minute amounts of salts 
(electrolytes). In this connection one naturally 
recurs to the observation of Bordet. which was 
mentioned in the preceding chapter, concerning 
the inaggln tin ability of micro-organisms so long 



COLLOIDS. 129 

as salt is withheld from the solution. This anal- 
ogy would suggest that the bacteria after their 
union with agglutinin may conduct themselves as 
colloidal particles. In the precipitation of colloids 
by salts it has been suggested that the salts so 
alter the electric condition of the colloidal parti- 
cles that their surface tension is decreased, and as 
a result of this change neighboring particles 
coalesce in such quantities as to produce a visible 
sediment. 

Xeisser and Friedberger have studied certain 
colloids, having in mind the similarity of their be- 
havior- to serum reactions. They found, for exam- 
ple, that two of our common dyes which are col- 
loids and bear opposite charges of electricity (eosin 
and Bismarck brown), give rise to a precipitate 
when the two are mixed. Furthermore, the spe- 
cific inhibition which may be obtained in the reac- 
tion with serum precipitins (see above) could also 
be realized with the eosin and Bismarck brown. 

The agglutination of bacteria and of red blood 
cells may also be accomplished with colloids. 
Landsteiner agglutinated erythrocytes with col- 
loidal silicic acid. 



CHAPTER XII. 



Bacteriolysis 

and Bacterio- 

lysin. 



Alexins, 



A. GENERAL PROPERTIES OF BACTERICIDAL 
SERUMS. 

Antibacterial, bactericidal and bacteriolytic are 
three terms which are used in a rather loose, inter- 
changeable way, although they are not strictly 
synonymous. A bactericidal serum is one which is 
able to kill bacteria, as the term implies ; if at the 
same time it dissolves the organisms it is bacterio- 
lytic. Inasmuch as some serums do kill bacteria 
without dissolving them (typhoid), while others 
have the dissolving power (cholera), the distinc- 
tion has a certain significance. In either case the 
serum is, of course, antibacterial. For lack of a 
more concise English term, bacteriolysis is used to 
designate the process in which bacteria, with or 
without solution, are killed by serums. Bacterioly- 
sin refers to the substances in serum which accom- 
plish this action. The means of determining the 
bactericidal power of a serum were indicated in 
Chapter Y, C. True bacteriolysis is best observed 
with the organism of cholera and its antiserum as 
described later under the title of the Pfeiffer ex- 
periment. 

Bacteriolysins are far more complex than anti- 
toxins, agglutinins and precipitins. One may best 
appreciate their nature as understood at present 
by tracing their development from the relatively 
simple alexins of Buchner. 

Following the investigations of Fodor, Behring 
and others, which showed that normal blood may 
kill bacteria in the test-tube, and after additional 



ALEXINS. 



131 



facts were obtained by Nuttall, Buchner demon- 
strated that it is not necessary to use the full blood 
in order to obtain the bactericidal action, but that 
serum alone has a similar effect. He spoke of the 
antibacterial substances collectively as alexins 
(substances which ward off), taking the reason- 
able view that natural immunity to bacteria de- 
pends on their presence in the body. The increased 
bactericidal power of the serum which develops 
during immunization or infection with certain 
micro-organisms goes hand in hand with the in- 
creased resistance of the individual against the 
infection. The alexins have undergone a specific 
increase; they are now immune alexins or, as we 
say to-day, immune bacteriolysins, and it is sup- 
posed that acquired immunity, in these instances, 
depends on their new formation. 

Alexins were very sensitive substances ; they dis- 
appeared spontaneously from serums in a few 
days, were destroyed by a rather low degree of 
heat (55° C), by acids and alkalies, and were 
active only in the presence of certain salts, espe- 
cially sodium chlorid. A striking feature of 
alexins, as distinguished from chemical bacteri- 
cides, was their marked selective action on bac- 
teria. The alexins of animal A might destroy one 
micro-organism readily and affect another little or 
none at all, whereas those of animal B might have 
different selective characteristics. 

Work which was instituted by Pfeiffer and de- 
veloped further by others led the way to a more 
correct understanding of the nature of alexins. 
Pfeiffer studied the bactericidal action of serums 
in the body of the living animal, i. e., in the peri- 
toneal cavitv. His most classic results were ob- 



Selective 
Action. 



The Phenome- 
non of Pfeiffer. 



132 INFECTION AND IMMUNITY. 

tained with the organism of cholera. A guinea- 
pig is .immunized against this microbe by injec- 
tions of the killed or living organisms. We have 
already learned of this process as that of active 
antibacterial immunization. When the animal is 
well immunized the experiment is begun by the 
intraperitoneal injection of a quantity of culture 
which would be fatal to an unimmunized animal. 
At intervals during the next twenty or thirty min- 
utes small amounts of peritoneal fluid are removed 
for .microscopic examination by means of fine 
pipettes which have been drawn out in the flame. 
The abdominal wall is punctured with the pi- 
pette through an incision in the skin and the 
fluid flows into the. tube by capillary attraction. 
A portion of the fluid is examined as a hanging- 
drop or dried on a cover-glass, fixed in the flame 
and stained with a dilute solution of carbol- 
fuchsin. In the hanging-drop it is first noticed 
that the organisms have lost their motility; the 
comma- and S-shaped forms soon become spherical 
and at first appear swollen and clear, whereas in 
later preparations they gradually decrease in size 
and show a very rapid vibrating movement, the so- 
called Brownian movement, which is purely physi- 
cal in nature. In the course of from twenty to 
thirty minutes the organisms have been completely 
dissolved. These changes may be followed in the 
stained specimens, in which the altered cells event- 
ually appear as fine red granules. 
The Experiment As Metchnikoff, Bordet and others have shown, 
the same result may be obtained without the inter- 
vention of the animal body, by mixing perfectly 
fresh anticholera serum with the vibrios and 
mounting as a hanging-drop preparation. The 



PFEIFFER EXPERIMENT. 



133 



slide must be kept at the temperature of the body 
by means of a warm stage. The reaction, how- 
ever, is far less vigorous than when it takes place 
in the peritoneal cavity and the solution of the 
cells may not be complete. No bacterium is so 
completely dissolved under these conditions as the 
vibrio of cholera, although the typhoid bacillus and 
similar organisms undergo some changes in their 
form. 

The experiment of Pfeiffer may also be con- 
ducted in the abdominal cavity of a non-immune 
guinea-pig by injecting anticholera serum in con- 
junction with the culture (passive antibacterial 
immunization) . This is the classic Pfeiffer experi- 
ment. The immune serum should be of such 
strength and should be given in such quantity that 
the animal is saved in spite of the ten fatal doses 
of culture which the typical experiment demands. 
Experiments brought to light a condition which 
seemed paradoxic; an old immune serum which 
had lost its bactericidal power as manifested in 
vitro, or one in which the alexins had been de- 
stroyed by a temperature of 60° C, showed its 
original protective power in the animal experi- 
ment. Furthermore, when an inactive immune 
serum was injected into the abdominal cavity, al- 
lowed to remain for a time and then withdrawn, 
its bactericidal power for experiments in vitro was 
found to be re-established. On the basis of these 
facts, Pfeiffer concluded that the specific sub- 
stance is present in the immune serum in an inac- 
tive form, and that it becomes active as a result 
of contact with living tissue cells, supposedly the 
endothelial cells of the peritoneum. According to 
this conclusion, an inactive sernm could become 



The Activation 
of an Inactive 
Serum by the 
Tissues. 



134 INFECTION AND IMMUNITY. 

active again only after its introduction into the 
body. 
inactivatiop It remained for Bordet to show, on the con- 
ovation! trary, that contact of the serum with living cells 
was not necessary to render it active for bacterici- 
dal experiments in vitro. It was sufficient to add 
to the heated immune serum a small amount of 
fresh normal serum from some normal animal, 
the quantity of normal serum which was used not 
being in itself bactericidal. Under these condi- 
tions, then, we have to do with two serums which, 
when combined, are bactericidal, but when sepa- 
• rated are inactive. The destruction of the active 
property of a serum by heat or by other means is 
called inactivation, and the re-establishment of its 
power by the addition of fresh normal serum is 
reactivation. The immune serum, when heated to 
55 to 60° C, loses something which is essential to 
its activity, and this something may be replaced 
by the normal serum. That the substance in the 
normal serum is identical with that which was de- 
stroyed in the immune serum is indicated by the 
fact that it is destroyed by the same degree of 
heat; a heated normal serum will not reactivate 
an immune serum. 
Two Substances The conclusion of Bordet that the bactericidal 
dai serum, power of a serum depends on the combined action 
of two substances has been substantiated by numer- 
ous investigators. These are the substances which 
in recent years have become familiar under the 
names of amboceptor and complement and their 
various synonyms (see p. 141ff). One of 
them, the amboceptor, is heat-resistant (thermo- 
stabile), i. e., it is not destroyed at 56° C, whereas 
the other, the complement, is susceptible to heat 



GROUP REACTION. 



135 



(thermolabile), being destroyed at that tempera- 
tare which killed the alexins of Buchner. The 
term alexin is still applied by some writers to the 
thermolabile substance (complement), its original 
significance having been modified. 

The specificity which prevails among antitoxins specificity. 
and agglutinins is found also in the action of bac- 
tericidal serums. When an anticholera serum is 
injected into the peritoneal cavity of a guinea- 
pig, protection is not afforded against other vibrios 
or other pathogenic organisms. The specificity is 
so great that the reaction of Pfeiffer may be used 
for the identification of bacteria. If one has in 
hand an unknown vibrio, its identity or non-iden- 
tity as the organism of cholera may be determined 
by injecting it, in conjunction with anticholera 
serum, into the peritoneal cavity of a normal 
guinea-pig; if the microbe is transformed into 
granules it is the vibrio of cholera, otherwise it is 
not. Other bacteria may be identified in a similar 
manner by the use of the proper serums. In spite 
of this high specificity, the group reaction may 
occur even with bactericidal serums. An anti- 
typhoid' serum, for example, shows its strongest 
bactericidal power for the typhoid bacillus, al- 
though it is at the same time more destructive for 
closely related organisms, as the colon bacillus, 
than a normal serum from the same species. By 
diluting the serum sufficiently the adventitious 
bacteriolysins are so nearly eliminated that the 
specificity of the serum for its homologous organ- 
ism becomes manifest. 

Bactericidal serums are not obtained with equal 
readiness for all micro-organisms. We are most 
familiar with those which are vielded bv immuni- 



Group 
Reaction. 



The Bacterici- 
dal Power in 
Relation to 
Immunity. 



136 INFECTION AND IMMUNITY. 

zation or infection with the microbes of cholera, 
typhoid, plague, the colon bacillus and related bac- 
teria. Many other bacteria, as the pneumococcus, 
streptococcus, tubercle bacillus and others, yield 
neither antitoxins nor bactericidal substances. In- 
asmuch as recovery from such infections is an ex- 
pression of acquired immunity, no matter how 
temporary it may be, it is evident that not all ex- 
amples of acquired immunity can be explained on 
the basis of the serum properties which we now 
recognize (see Chapter V, C). This will be re- 
ferred to again in relation to phagocytosis (Chap- 
ter XIV). 

Experiments of some importance have to do 
with the ability of bacteria to absorb the homolo- 
gous bactericidal substance from a serum when the 
two are mixed in test-tubes. Hence, if natural 
antibacterial immunity depends on the bacterioly- 
sin which is present in the circulation, a large 
mass of the bacterium when injected intravenously 
should absorb or fix the bactericidal substances ; as 
a consequence, serum which is drawn later should 
show a great decrease in its bactericidal power for 
the organism which was injected. Although re- 
sults of this nature have been obtained by a num- 
ber of competent investigators, they are not with- 
out exception. In the same connection fatal infec- 
tions should be accompanied by a decrease of the 
natural bactericidal power of the serum for the 
organism involved. This has been found to be true 
in man in relation to plague, and in some animal 
infections. 
TheEffertof In a preceding chapter micro-organisms were 
divided, first, into those which secrete soluble tox- 
ins, immunization with which causes the forma- 



Bactericidal 
Serums on 
Endotoxins. 



EFFECT OX EXDOTOXIXS. 137 

tion of antitoxins, and, second, those which do not 
secrete such toxins and for which no manipula- 
tions known at the present time are successful in 
stimulating to the formation of antitoxins. These 
lines, however, can not be drawn sharply, for there 
are a few microbes which, according to manipula- 
tion, cause the formation of either an antitoxic 
serum or a bactericidal serum. In general it may 
be said that the character of the serum depends on 
the bacterial constituent which is used for immuni- 
zation. If the diphtheria bacillus itself, or the 
pyocyaneus bacillus, is injected, the toxin having 
been washed away, bactericidal serums are formed, 
whereas if toxins alone are introduced, antitoxins 
are the result. After all, it seems plain that the 
bacteria of the second group must be pathogenic, 
because of toxic substances which they carry with 
them into the body. In view of the fact, however, 
that they do not secrete soluble toxins in culture 
media, it is held that their toxic properties are in- 
tegrally associated with the bacterial protoplasm; 
they are the endotoxins spoken of previously. 

The question naturally arises : Does a bacteri- 
cidal serum in dissolving or killing its homologous 
organism neutralize the endotoxin at the same 
time? On the basis of very positive experiments 
which have been performed, especially by Pfeiffer, 
it is evident that the serum has no such action. In 
the experiment of Pfeiffer, one may inject into the 
abdomen a sufficient quantity of anticholera serum 
to kill all the organisms which have been intro- 
duced, and yet the animal may die with the intoxi- 
tion of cholera. Furthermore, if one considers a 
culture of the cholera vibrio, which has been killed 
by heat, as representing so much cholera toxin. 



138 



INFECTION AND IMMUNITY. 



Origin of 
Bactericidal 
Substances. 



Standard- 
ization. 



anticholera serum protects against no more of it 
than does the same quantity of normal serum. It 
is believed that anticholera and similar immune 
serums may even increase intoxication by dissolv- 
ing the bacteria and thus liberating an excess of 
endotoxin. 

We have little positive knowledge concerning the 
organs which form the bactericidal substances in 
acquired immunity. Pfeiffer and Marx, in rela- 
tion to cholera, and Wassermann in typhoid, found 
that the spleen and the hemopoietic organs in gen- 
eral contain the immune bodies in greater concen- 
tration than the blood serum, and in immunization 
experiments the bodies may be demonstrated in 
these organs at a time when they are absent from 
the circulation. This fact is generally accepted as 
proof of their formation at these points. Wasser- 
mann and others have demonstrated the presence 
of complement in the leucocytes, and Metchnikoff 
holds that it is produced only by such cells. 
. The standardization of bactericidal serums is at 
present more of theoretical than of practical in- 
terest, because of their limited therapeutic use. 
Their values can not be determined with the ac- 
curacy with which one measures a unit of anti- 
toxin. One may deliver from a pipette a definite 
quantity of toxin and if the toxin has been well 
preserved the same quantity may be obtained at 
any subsequent time. On the other hand, it is impos- 
sible to preserve a culture of living bacteria so that 
the number of the organisms and the virulence 
of the culture remain constant, nor will two cul- 
tures made at different times contain the same 
number of cells in a given volume. Hence, stand- 
ard cultures which are necessary for the systematic 



STANDARDIZATION. 139 

valuation of serums are not easily available. One 
may use a definite volume of a bouillon culture of 
an organism which has grown for a certain number 
of hours, but in all likelihood no two cultures 
would contain the same number of organisms. 
PfeifTer uses the normal loop which has been men- 
tioned, i. e.. one which will take up from a surface 
of agar two milligrams of the bacterial mass. The 
culture must have grown for a definite period, 
eighteen to twenty-four hours. Tests having some 
value may be made in the test-tube with the fresh 
or complemented serum. This, however, gives one 
only the bactericidal power as it is manifested out- 
side the body, and it may not be a correct index of 
the protective power of the serum when it is in- 
jected into the living animal. For the test-tube 
experiment various dilutions of the serum are 
made, as 1 to 10, 1 to 100 and 1 to 1,000, and a 
similar quantity of each dilution, properly comple- 
mented, is mixed with a given mass of the culture ; 
the mixtures are then placed in the thermostat for 
a number of hours. At the end of this time plate 
cultures are made from each of the mixtures, the 
plates put aside for twenty-four hours, and the 
colonies which have developed are then counted. 
The quantity of serum required to kill all the bac- 
teria may be taken as the basis for computing its 
bactericidal value. 

When the protective power of the serum is de- 
termined by animal experiment it is not essential 
to use the serum when fresh; in fact, the native 
complement in the immune serum may be disre- 
garded, or, preferably, it may be destroyed by heat. 
If the latter procedure is adopted, or if an old 
serum is used in which the complement has de- 



140 INFECTION AND IMMUNITY. 

generated, its reactivation is accomplished through 
the complement which is present in the body of the 
experiment animal. It will appear in more detail 
in the following pages that a given antiserum re- 
quires a particular complement for its reactiva- 
tion, and that this complement may be present in 
some animals and absent in others. 

To find the value of anticholera serum Pfeiffer 
prepares dilutions similar to those mentioned 
above, and to the same quantity of each dilution 
adds ten fatal doses of a virulent culture of the 
vibrio of cholera. These are injected into the 
peritoneal cavities of guinea-pigs and after periods 
of forty to sixty minutes hanging-drop prepara- 
tions are made from the peritoneal fluid of each 
animal to determine the formation of the charac- 
teristic granules ; the highest dilution which causes 
this change in the cells stamps the value of the 
serum. The animal must at the same time be pro- 
tected against the ten fatal doses of the culture. 

The value of an antityphoid serum may be de- 
termined in the same way, the result being judged 
by the protection which is afforded the animal 
rather than by the formation of granules. 

Antityphoid, antiplague, and some other serums 
are also tested by injecting the serum twenty-four 
hours in advance of the culture. 

It is necessary to know the virulence of a cul- 
ture with which an antiserum is tested. It is pos- 
sible to maintain some organisms at a rather con- 
stant virulence by passage, i. e., infecting animals 
with the microbe and recultivating it from the 
tissues. With others, abundant controls must be 
made at the time the serum is tested in order to 
know at that moment the precise virulence of the 



AMBOCEPTOR AXD COMPLEMENT. 141 

culture. In all probability it requires more serum 
to protect against very virulent cultures than 
against those of less virulence. 

In contrast to the specific immunization which Non-Specific 

, ... . . Increase in 

may be accomplished with an immune serum, it Resistance. 
is important to recognize that a non-specific in- 
crease in resistance may be caused by the injection 
of a number of substances, which in the test-tube 
have no destructive action on the bacteria. Issaeff 
injected into the peritoneal cavity such substances 
as bouillon, tuberculin and sterile urine, and found 
the resistance of the animals increased to perito- 
neal inoculation of virulent organisms. Normal 
serum from another animal has a similar effect, 
but, in this instance, the bactericidal substances of 
the foreign serum may be a factor in the new re- 
sistance. Supposedly, this non-specific resistance 
is local, and it appears to depend on the attraction 
of an increased number of phagocytes and of addi- 
tional complement to the peritoneal cavity. The 
suggestion recently made that preceding laparot- 
omy nucleinic acid be injected into the abdominal 
cavity, in order to increase the local resistance, has 
its foundation in the experimental work just cited. 

B. AMBOCEPTORS AXD COMPLEMENTS. 

The simplicity of hemolytic experiments and the Experimental 
rapidity with which they may be performed and o?y"ins. f " em 
terminated have rendered hemolytic serums par- 
ticularly useful in the study of amboceptors and of 
complements, for we are to understand that such 
serums are toxic to erythrocytes only because of 
the amboceptors and complements which they con- 
tain. The most important facts which have been 
learned concerning the action of hemolytic serums 



Technic of 
Hemolytic 



142 INFECTION AND IMMUNITY. 

have been found to hold true for bactericidal 
serums as well; hence it is an indifferent matter 
if principles which are common to both are illus- 
trated by frequent references to serum-hemolysins. 
The corpuscles for hemolytic experiments are 
Experiment, obtained by the defibrination of freshly-drawn 
blood and the removal of the fibrin. Usually they 
are made into a 5 per cent, suspension by dilution 
with isotonic (physiologic) salt solution. Inas- 
much as the serum which is present may interfere 
with the action of the complement or amboceptors 
of the hemolysin, it is customary to remove it by a 
washing process. The 5 per cent, emulsion, or the 
undiluted blood is centrifugated, the overlying 
fluid drawn off by means of a pipette and substi- 
tuted by fresh salt solution; the corpuscles are 
thoroughly mixed with the new solution and the 
process of centrifugation repeated, the corpuscles 
finally being diluted to the original volume with 
salt solution. After from two to four washings 
any residual serum usually may be disregarded. 
To test the hemolytic power of a serum one meas- 
ures identical quantities of the 5 per cent, washed 
blood into each of a series of test-tubes by means 
of. a graduated pipette and then adds increasing 
quantities of the serum to succeeding tubes. All 
tubes are then diluted to equal volumes by means 
of salt solution, as it is of some importance to 
maintain a uniform concentration of the cor- 
puscles. The contents of the tubes are mixed 
evenly by shaking and the series is placed in the 
thermostat for about two hours; this temperature 
is necessary for complete and rapid action of the 
toxic substances. At the end of this time the tubes 
are placed in the ice chest and left over night in 



HEMOLYSIS. 



143 



order that the cells may settle to the bottom, or 
sedimentation may be accomplished at once by 
centrifugation. 

In either case, the overlying fluid is colored red Hemolysis. 
by the dissolved hemoglobin in proportion to the 
extent of destruction of the erythrocytes. In case 
solution has been complete, the sediment is indis- 
tinct and colorless, being made up only of the 
stromata of cells, whereas in the tubes showing 
only partial hemolysis the sediment is red and has 
an indirect quantitative ratio to the coloration of 
the overlying fluid. By suitable variations in the 
amounts of serum used in different tubes, its 
exact dissolving dose for the given volume of cor- 
puscles may be determined. Although the term 
hemolysis is a perfectly proper one, we are to un- 
derstand that serums cause solution of the hemo- 
globin, but not solution of the whole cell ; we speak 
loosely of solution of the corpuscles. 

After Bordet had shown the analogv between similarity Be- 
bactericidal and hemolytic serums, and after the cidai and Hem - 
phenomena of inactivation and reactivation had ° yt,c Act,on ' 
been developed by Bordet and Metchnikoff, Ehrlich 
and Morgenroth undertook the study of ambocep- 
tors and complements as they occur in hemolytic 
serums. The facts ascertained by them and the 
methods of research which they devised have pro- 
vided many investigators with a starting point for 
work of the highest importance concerning the 
bactericidal serums and antibacterial immunity, 
and their interpretations, moreover, served to ex- 
tend the side-chain theory of immunity to its pres- 
ent comprehensive limits. 

For the sake of convenience one may speak of a 
heated immune senim. or one in which the com- 



144 INFECTION AND IMMUNITY. 

Solutions of plement has become inactive from age, as a solu- 
and b °compie- tion of amboceptors, disregarding temporarily the 
ments. agglutinins, precipitins and perhaps other bodies 

which the serum contains. Also, since fresh nor- 
mal serums are rich in complements and usually 
contain but a small amount of any one amboceptor, 
they may conveniently be considered as solutions 
of complements; yet normal serums may not be 
considered as pure complement and used as such 
in unlimited quantities for actual experiments, be- 
cause of the bacteriolysins and hemolysins which 
many contain. Only a quantity of the normal 
serum which in itself is not toxic for the cell 
may be used for complementing purposes, and this 
may be as low as, or lower than, 0.1 c.c. for a par- 
ticular experiment. 
The Absorption As pointed out in the preceding chapter, the 

of Amboceptors , . -, , . „ , , ■, j , . 

by cells. combined action 01 amboceptor and complement is 

necessary for the cytotoxic action of a serum. In 
view of the fact that the toxic power is lost by ex- 
posure to that temperature which destroys comple- 
ment, it seems that the latter is the actual dis- 
solving or toxic substance, whereas the ambocep- 
tor must play some intermediary role. Investiga- 
tions have shown that the two act together in a 
very definite manner in that the absorption of the 
amboceptors by the cells is a prerequisite for the 
absorption and action of the complement. This 
may be verified by simple experiments. Mix 
erythrocytes with the homologous amboceptors, 
and after a period of from twenty to thirty min- 
utes centrifugate the mixture and remove all the 
free serum from the cells by repeated washings 
with isotonic salt solution. If the cells are again 
suspended in salt solution and a small amount of 



M EC H AX ISM OF HEMOLYSIS. 145 

complement is added and thoroughly mixed, the 
hemoglobin is dissolved out; a control must, of 
course, show that the complement alone has not 
the dissolving power. The result indicates that 
the erythrocytes during their contact with the im- 
mune serum had absorbed or combined chemically 
with the amboceptors, and that the latter remained 
attached to the cells in spite of the washings to 
which they were submitted. 

It would seem that the union of amboceptor Sensitization 
with cell has the effect of rendering the latter sus- 
ceptible to the action of complement, and for this 
reason amboceptor-laden cells are spoken of as 
sensitized cells. Hence, according to the cells and 
serums employed, we may refer to sensitized 
erythrocytes, sensitized bacteria, etc. The experi- 
ment is called the sensitizing, absorption or bind- 
ing experiment. An immune serum may be de- 
prived of all its amboceptors in the binding ex- 
periment if a sufficient quantity of cells has been 
used, and it would thereby be rendered incapable 
for further reactivation by the subsequent addition 
of complement. 

If, instead of performing the experiment in the Order of Action 

j M n ,1 . t 1 1 i of Amboceptor 

manner described, the process is reversed so that andcompie- 
the corpuscles are first treated with the solution ment * 
of complement and then with the amboceptors, the 
corpuscles are not hemolyzed. During the wash- 
ing process the complement is entirely separated 
from the cells, and from this fact it is clear that 
direct union between corpuscle and complement 
does not occur; only sensitized cells take up com- 
plement. 

The question as to whether the corpuscles in 
taking up amboceptors do so by chemical combina- 



X46 INFECTION AND IMMUNITY. 

Cytophiious tion or by physical absorption has been contended 
of the Am- with some vigor. Ehrlich believes that the process 
boceptor. j g one Q £ c ]j eiI1 i ca ]_ union, and if one adheres to this 
view it becomes necessary to assign binding or 
haptophorous groups both to the red blood cells 
and to the amboceptors. In contrast to another 
haptophore which the amboceptor possesses and 
which will be described below, that one which 
unites with the cell is called the cytophiious hapto- 
phore. The haptophore of the erythrocyte which 
enters into the union is an essential part of a re- 
ceptor of the red cell, consequently we say that the 
amboceptor unites with a receptor of the corpuscle. 
TheAbsorptjon The heating of serum to 56° C. provides one 
in the cold, means of apparent isolation of the amboceptor 
from the complement, but this is not a true isola- 
tion in that complement is merely rendered inac- 
tive by the heat rather than totally eliminated. 

Ehrlich and Morgenroth devised a method by 
which the amboceptors may be separated from a 
fresh immune serum without in any way injuring 
the complement. This is accomplished by per- 
forming the binding experiment, already alluded 
to, at a low temperature. The serum, containing 
both amboceptors and complement, is cooled to 0° 
C. or slightly above, by means of a freezing mix- 
ture of salt and ice. A suspension of the homolo- 
gous corpuscles is cooled to the same point, the 
serum is added and the mixture maintained at 0° 
to 4° C. for fifteen to twenty minutes. At the 
end of this time the sensitized cells are removed 
by immediate centrif ligation at a low temperature, 
and are washed entirely free from serum by the 
use of ice-cold salt solution. If the low tempera- 
ture has been adhered to risjorouslv and the work 



UNION WITH CELLS. 



147 



done quickly, the corpuscles are not laked during 
the manipulations in spite of the presence of both 
amboceptors and complement. Furthermore, the 
washed sensitized cells remain intact even when 
their temperature reaches that of the thermostat, 
whereas if some fresh normal serum or the serum 
from which the amboceptors were absorbed is 
added, they undergo hemolysis as readily as when 
treated with the active immune serum. The 
original immune serum is now a solution of com- 
plement, and fresh corpuscles which are added to 
it are not dissolved because of the absence of ambo- 
ceptors. 

These results show the following important 
facts : Amboceptor and complement exist side by 
side in an immune serum, not as a united sub- 
stance. Union of amboceptor with cell is inde- 
pendent of complement, the latter being taken up 
only after the amboceptor-cell reaction has oc- 
curred. Amboceptors unite with cells at a low 
temperature, whereas complement requires a 
higher temperature for its union and for the fer- 
ment-like activity by which it dissolves or kills the 
cells. 

That constituent of the amboceptor which 
unites with the cell has been referred to as the 
cytophilous haptophore. Ehrlich and his follow- 
ers believe that complement in establishing con- 
nection with the cells does so by combining with a 
second haptophore of the amboceptor, after the 
latter has sensitized the erythrocyte or bacterium. 
Hence, an amboceptor has, as the name implies, 
two receiving groups or haptophores, the second 
being the complementophilous haptophore (Fig. 
7). It is hardly desirable to discuss various ex- 



Complemento- 
philous Hapto- 
phore of Am- 
boceptor. 



148 INFECTION AND IMMUNITY. 

periments which furnish additional evidence of the 
amboceptor nature of the thermostabile body. The 
observed phenomena allow one to assign to it the 
two haptophores mentioned. 
Action of There is a conflict of ideas as to the nature of 
the change produced by the amboceptors, as a re- 
sult of which the cells are made susceptible to the 
action of complement. Bordet speaks of the am- 
boceptor as the substance sensibilisatrice, the sen- 
sitizing substance; and his conception of the ac- 
tion of the two substances he has compared rough- 
ly to the opening of a lock for which two keys are 
demanded. One key, amboceptor, is needed to 
prepare the lock for the action of the second key. 
complement, the latter being the one which really 
opens it. 

Metchnikoff applies the name fixator to the 
thermostabile body, having in mind the action of 
a mordant in preparing tissues or other substances 
for the reception of a dye; this differs little from 
preparator, the word used by G-ruber. 

The idea of Ehrlich, however, is distinctly at 
variance with the conceptions mentioned, for he 
sees in the union of amboceptor with cell nothing 
more than the introduction of a new chemical 
affinity, i. e., one which attracts complement, and 
this new affinity does not lie in the cell itself, but 
rather in the amboceptor (complementophilous 
haptophore) after the union has occurred. Hence, 
the terms intermediary body (Zivischenlcdrper) , 
copula of Miiller, and desmon of London, are 
words which carry with them the meaning that the 
amboceptor first unites with the cell and then acts 
as a linking substance through which complement 
finally is put in relation to the cell. This also is 



COMPLEMENTOID. 



149 



Complement. 



the meaning embodied in the amboceptor of 
Ehrlich, the word indicating more accurately his 
conception of the method by which the substance 
acts as an intermediary body. 

If we consider it established that in the process structure of 
of cytolysis union occurs between complement and 
amboceptor we must at the same time assign a 
haptophorous group to complement. Union would 
be impossible without it. Corroborative proof of 
the existence of this haptophore lies in the fact 
that immunization with complement results in the 
formation of anticomplement, a prerequisite for 
which is union of complement with cell receptors 
in the immunized animal ; and this union, it seems 
necessary to assume, takes place through a binding 
group. The mere possession of a haptophore, how- 
ever, does not account for the ferment-like activity 
of complement. The latter characteristic resides 
in the so-called zymotoxic group; hence, comple- 
ment, having a binding and a toxic group, has a 
structure like that of a toxin. 

Somewhat loosely we have said that the inactiv- 
ity of a serum which has been heated to 56° C. 
depends on destruction of the complement. This 
is not strictly true, however, for such treatment 
destroys only the zymotoxic group, the haptophor- 
ous constituent remaining uninjured. Comple- 
ment altered in this respect is called complemen- 
toid, and it is analogous to toxoid, agglutinoid and 
precipitoid. Two essential facts go to show that 
this is the principle change wrought by heating. 
First, the fact stated above, that immunization 
with complementoic], causes the formation of 
anticomplement. Second, complementoid may 
exceed true complement in its affinity for the 



Complemen- 
toid. 



L50 INFECTION AND IMMUNITY. 

amboceptor, and if sensitized cells are treated with 
a serum containing a mixture of complement and 
complementoid, the latter may occupy completely 
the complementophilous haptophores of the ambo- 
ceptors and thus may block the way for action on 
the part of complement. This is again the spe- 
cific inhibition which has been mentioned in con- 
nection with toxoids, agglutinoids and precipi- 
toids. This is the C omplementoid-V erstbpfung of 
Ehrlich. . * 

Formation of The amboceptor, as the characteristic property 

Amboceptors. P -, . . . n -, pi i ."• 

oi a bactericidal or of a hemolytic serum, is a spe- 
cific product of the immunization, whereas the 
amount and character of complement in the im- 
munized animal undergoes little or no change. 
We are, -of course, obliged to consider the ambo- 
ceptors as a product of the cells of the body. In 
the terminology of Ehrlich, they are discarded cell 
receptors, and with their two haptophores repre- 
sent a more complex structure than either the re- 
ceptors of antitoxin or agglutinin; the latter are 
uniceptors; the former amboceptors, and because 
of their higher differentiation Ehrlich has called 
them receptors of the third order (Fig. 7). 

When micro-organisms gain entrance to the 
body. they are killed and dissolved in considerable 
masses. As a result of the solution, certain bac- 
terial constituents reach the circulation, and 
among them are molecules or receptors which pos- 
sess haptophores capable of uniting with a par- 
ticular type of amboceptor, the latter being an in- 
tegral part of some tissue cells. This union hav- 
ing taken place, an affinity for circulating com- 
plement may be created as in the test-tube experi- 
ments. We have thus the possibility of stimula- 



FORMATION OF AMBOCEPTORS. 151 

tion of the cell by the bacterial constituent itself 
as a toxic or unusual food substance, or the toxic 
action ma}' be caused by products of disintegra- 
tion of the bacterial substance, the disintegration 
having been accomplished by the digestive action 




Fig. 7. — Graphic representation of receptors of the third 
order, and of some substance uniting with one of them, 
c, Cell receptor the third order, an amboceptor ; e, one of the 
haptophores of the amboceptor, with which some food sub- 
stance or product of bacterial disintegration, f, may unite ; 
g, the other haptophore of the amboceptor with which com- 
plement may unite ; K, complement ; h, the haptophore, and 
z, the zymotoxic group of complement. From Ehrlich's 
"Schlussbetrachtungen," Nothnagel's System of Medicine, 
vol. viii. 

of the complement which was taken up by the am- 
boceptor. The effect is that of an unusual stimu- 
lation, in response to which the cell, if not fatally 
injured, reproduces many amboceptors correspond- 
ing to the type which was occupied or injured. As 
in the formation of other antibodies, the new- 



152 



INFECTION AND IMMUNITY. 



Specificity of 
Bactericidal 
Amboceptors 
and Comple- 
ments. 



Bacterial 
Receptors. 



formed amboceptors reach the general fluids of the 
body. 

Concerning the specificity of serum-hemolysins 
and serum-bacteriolysins for their homologous 
cells, we, of course, refer to the specificity of the 
whole amboceptor-complement complex. It is nec- 
essary to throw the responsibility on both sub- 
stances, because of the variations which exist 
among complements as well as among ambocep- 
tors. Inasmuch, however, as the heat-resistant 
body alone is increased during immunization or 
infection, the greater part of the specificity- would 
seem to depend on the nature of the amboceptor 
rather than on that of complement. 

All bacteria which stimulate to the formation 
of bactericidal serums do so because of certain re- 
ceptors which they possess. These are, of course, 
analogous to the receptors of erythrocytes which 
cause the production of the hemolytic bodies in 
serum. Bacteria have, in addition, many other re- 
ceptors, some of which cause the development of 
agglutinins. In the latter instance we speak of the 
agglutinogen^ receptors of the cells, but there is 
no" name of equal convenience which is used to 
designate the receptors which stimulate to the 
formation of amboceptors. N"o two micro-organ- 
isms contain an identical receptor apparatus : if 
the contrary were the case their antiserums would 
coincide in their bactericidal action. Therefore, the 
cell receptors (amboceptors) with which they unite 
during immunization differ correspondingly in 
their cvtophilous haptophores. The cytophilous 
haptonhore of the typhoid amboceptor finds its 
specific counterpart in the typhoid bacillus, and 
finding no such counterpart in the vibrio of chol- 



COMPLEMENT AND ANTWOMPLEMENT 153 

era, the latter can not be sensitized by the anti- 
typhoid serum ; on this fact depends the specificity 
of the serum. This conception does not interfere 
with the explanation of the group reaction among 
bactericidal serums, for it is conceivable that the 
colon bacillus, for example, has, in addition to 
those receptors which characterize the organism, a 
small percentage of receptors which are identical 
with those characterizing the typhoid bacillus. In 
accordance with this possibility an antityphoid 
serum may well, as it does, show some increased 
bactericidal power for closely related organisms. 
Hence the explanation of group bacteriolysis is 
identical with that of group agglutination. 

There is a wide difference of opinion regarding Multiplicity of 
the unity of complement, or alexin, its synonym. Complemente - 
Bordet and his followers stand for the unity of the 
alexins, and their position rests on the fact that a 
given normal serum may be used to activate many 
different amboceptors. We should appreciate that 
this phenomenon might depend on the broad range 
of action of a single complement, or on the pres- 
ence of different complements each being specific 
for a particular amboceptor. Ehrlich and his 
school take the latter view and have actually dem- 
onstrated a multiplicity of complements in a few 
instances. Ehrlich and Sachs treated fresh nor- 
mal serums (complement) in various ways, such 
as digestion with papain, partial destruction with 
alkalies, heat, etc.. and were able by those moth oris 
to destroy the complement for one kind of ambo- 
ceptor, while the serum still retained its power for 
activating other amboceptors. Accordingly, it 
seems clear that the ability of a normal serum to 
activate a given amboceptor depends not only on 



plements. 



154 INFECTION AND IMMUNITY 

the presence of complement in a general sense, but 
on the presence of a suitable complement, i. e., one 
the haptophore of which corresponds to the com- 
plementophilons haptophore of the amboceptor. 
This point is of great importance in reference to 
the treatment of infections diseases with antibac- 
terial serums, for the efficacy of the serum would 
seem to depend on the introduction of suitable 
complement in conjunction with the amboceptors, 
or on the existence of such complement in the body 
of the patient. 
Antkom- Added proof of the multiplicity of complements 
has been obtained by experiments with anticom- 
plements. As stated, the latter are obtained by 
immunization of suitable animals with normal or 
immune serums which contain complement or com- 
plementoid. When they are mixed with the homolo- 
gous complements the haptophores of the latter 
are bound by means of the haptophores of the anti- 
complements. The evidence of this union lies in 
the fact that a complement which has been treated 
with its specific anticomplement is no longer able 
to activate the appropriate amboceptor. With 
properly selected serums, it may be shown that a 
given anticomplement will neutralize a comple- 
ment which is specific for one amboceptor, but will 
have no effect on another complement which acti- 
vates a different amboceptor. Hence, complements 
differ at least in this respect that not all have iden- 
tical haptophores. Immunization with leucocytes, 
cells which contain complement, also causes the 
formation of anticomplement. Both natural and 
acquired antibacterial immunity may be lowered 
by the injection of anticomplement which is ho- 
mologous to the complement of the animal. 



POLYCEPTOR 8. 



155 



Some time ago Ehrlich expressed the opinion 
that an amboceptor in certain cases may have more 
than one complementophilons haptophore; in 
other words, that it may be a polyceptor rather 




Fig. 8. — Illustrating the amboceptor with more than one 
complementophilous haptophore (a polyceptor). a, Cell re- 
ceptor ; b, cytophilous haptophore of the amboceptor ; c, the 
dominant complement ; d, the non-dominant complements 
* , The haptophore of the amboceptor for the dominant com- 
plement; /3, those for the non-dominant complements. (From 
Ehrlich and Marshall.) 

than an amboceptor. This has again been empha- 
sized recently by way of explaining the ability of 
an amboceptor to absorb from a normal serum not 
only the complement which serves to activate the 



156 INFECTION AND IMMUNITY. 

amboceptor, but also others which happen to be 
present in the serum. The former is spoken of as 
the dominant complement and the latter as non- 
dominant complements. Figure 8 is an illustra- 
tion of such a polyceptor. 
Antiam- If one immunizes with an immune serum the 

boceptors. -, , • -i * • -i , • 

product is spoken of m a general way as an anti- 
immune serum. The latter contains, as stated, 
anticomplement, and through the agency of this 
substance the antiserum antagonizes the action of 
the serum which was used for the immunization. 
Inasmuch, however, as the immune serum contains 
amboceptors also, the antagonistic action of the 
antiserum may depend, in part, on the presence of 
antiamboceptors. Differentiation between the ac- 
tion of anticomplement and antiamboceptor is dif- 
ficult, but it may be accomplished in certain cases 
by appropriate binding experiments. Serum 1, an 
inactive hemolytic serum, i. e., a solution of ambo- 
ceptors and complementoid, is treated with serum 
2. Serum 2 has been obtained by immunization of 
an animal with serum 1, and contains anticomple- 
ment and possibly antiamboceptors. If serum 2 
contains only anticomplement, it will have no ef- 
fect on the amboceptors of serum 1, when the two 
are mixed. The amboceptors are free to sensitize 
corpuscles which may be added, and the latter when 
sensitized undergo hemolysis in the presence of 
complement. If, however, serum 2 contains anti- 
amboceptors, either the cytophilous or the comple- 
mentophilous haptophore of the amboceptor will 
be bound. In either case corpuscles which are 
added subsequently would not appear as sensitized, 
for if the cytophilous haptophore had been bound 
by antiamboceptor union between cell receptor and 



DIVERSION OF COMPLEMENT 



157 



amboceptor could not occur'; and if the comple- 
inentophilous haptophore had been preoccupied 
complement would have no effect even if the ambo- 
ceptors had united with the cells by their unbound 
cytophilous haptophores. Ehrlich and Morgenroth 
demonstrated such antiamboceptors for certain 
hemolytic serums, and it was their belief that they 
combine with the cytophilous rather than with the 
complementophilous haptophore of the ambo- 
ceptor. However, Ehrlich has recently been able 
to prove the occurrence of an antibody for the com- 
plementophilous haptophore in one case. Pfeiifer 
also reports the demonstration of antiamboceptors 
for the specific amboceptors of anticholera serum. 
The possibility of antiamboceptor formation is one 
of practical bearing, in view of the fact that the 
prolonged treatment of a patient with a bacteri- 
cidal serum may result in the development of such 
antibodies. If present in sufficient amount they 
would combine with new amboceptors which were 
injected and thus deviate the latter from the bac- 
teria. 

A phenomenon equally of theoretical and prac- 
tical importance has to do with the so-called diver- 
sion (AblenJcung) of complement. It has been 
found that the action of a bactericidal or hemolytic 
serum is lessened, if a great excess of amboceptors 
over complement is added. To explain this fact 
Neisser and Wechsberg have supposed that when 
so many amboceptors are present that all can not 
be taken up by the cells, those which remain free 
are able to combine with some of the complement 
which is present and thus prevent the accession of 
the latter to the sensitized cells ; that is to say, the 
complement is diverted from its natural course of 



Danger of 
Formation 
of Antiam- 
boceptors. 



Diversion of 
Complement 
and Its Theo- 
retical Danger. 



158 INFECTION AND IMMUNITY. 

action (Fig. 9). This amounts to a protection of 
the sensitized cells from the action of the comple- 
ment. The phenomenon led Wechsberg to sug- 
gest that in the therapeutic administration of bac- 
tericidal serums it may be possible to give too 
much of the serum. Although diversion of com- 
plement is a demonstrated fact, its importance in 
serum therapy is perhaps not definitely settled. 
Hemolytic Am : It is of interest that amboceptors are widely dis- 
tributed in the animal kingdom, and that in cer- 
tain instances they may be demonstrated in the 
secretions. It has long been known that the 



boceptors of 
Venom. 





Fig. 9. — Illustrating diversion of complement. The free 
amboceptors have combined with the available complement, 
and thereby prevented the latter from activating the am- 
boceptors which have united with the bacterial cell. (From 
Neisser and Wechsberg.) 

venoms of serpents owe a great deal of their tox- 
icity to their power of destroying red blood cells.* 
A given venom may contain several toxic sub- 
stances, and the poisons of different serpents by 
no means coincide in their toxic properties. Cobra 
venom has at least two distinct toxins, one for the 
nervous tissue and one which dissolves erythro- 
cytes, the neurotoxin having the greater patho- 
genic significance; it, moreover, agglutinates red 
blood corpuscles. The venom of the rattlesnake, 
on the other hand, is neurotoxic to a less degree, 
but has a pronounced influence in causing capil- 

* See also part IT, Chapter 3, concerning venoms. 



ENDOCOMPLEMENT. 159 

lary hemorrhages. The latter power Flexner as- 
cribes to a toxin for endothelial cells, which he 
calls hemorrhagin. Through the works both of 
Flexner and Noguchi and of Kyes, facts were 
learned concerning the hemolytic toxin of cobra 
venom, which may be of great importance in prob- 
lems of general immunity. It seems that the 
hemolysin of venom is an amboceptor rather than 
a toxin of the usual nature, and that the aid of 
complement is necessary for its toxic action. The 
venom itself contains only the amboceptors, hence 
the toxicity of the substance depends on its being 
complemented after it is introduced into the body. 
The possession of suitable complement, therefore, 
is a source of danger in this instance rather 
than a means of protection for the individual. 
One may very well suspect that a similar relation- 
ship is possible in connection with other sub- 
stances which are as yet unknown. 

A fact of additional importance is that the am- Endocom- 
boceptor finds suitable complement not only in the 
serum of the animal but it may also be activated 
by a complement which the erythrocytes them- 
selves contain. Kyes speaks of the latter as endo- 
complement, i. e., endocellular complement. 

In attempting to discover the nature of the com- Lecithin. 
plement which is present in the erythrocytes, vari- 
ous substances existing normally in the red cells, 
as cholestrin and lecithin, were obtained in pure 
form and their activating power for the cobra am- 
boceptors was tested in reagent-glass experiments. 
From this work it was learned that lecithin, a defi- 
nitely known chemical substance, has the activat- 
ing power, and it was, therefore, assumed that the 
endocomplement of erythrocytes is nothing more 



160 



IXFECTION AXD IMMUNITY. 



or less than lecithin. All erythrocytes contain 
lecithin, yet not all are equally susceptible to the 
action of venom in the absence of serum comple- 
ment ; that is to say, endocellular lecithin does not 
act as complement with equal readiness in all 
cases. In order to explain this variation it was 
necessary to assume that the lecithin in the cells 
of one animal may be more available as comple- 
ment because it is bound to other cell constituents 
only in a very loose way, whereas in more resistant 
cells the union is of a firmer nature. 
Cobra-iecithid. The relationship between cobra amboceptors and 
lecithin seems to be a very definite one, for Kyes 
was able to obtain a union of the two without the 
intervention of erythrocytes. The resulting sub- 
stance, the cobra-lecithid of Kyes, is a completed 
toxin and needs no further activation. We have 
yet to learn of the true nature of this new com- 
pound, the discovery of which seemed to augur a 
more intimate chemical knowledge of the sub- 
stances which are concerned in immunity. 
Hemolysis by Lecithin is a colloid, and in this connection it is 
Action of interesting to note that it may be used in combina- 
co iioids. ^ on yftfa g^ji another colloid in such manner that 
the hemolysis which they cause is analogous to 
that produced by hemolytic amboceptors and com- 
plements. Landsteiner tried the effect of col- 
loidal silicic acid on erythrocytes which were en- 
tirely freed from serum, with the result that the 
corpuscles were agglutinated under its influence. 
It developed further, however, that colloidal silicic 
acid not only acts as an agglutinin, but also simu- 
lates a hemolytic amboceptor, and in the latter 
capacity it may be activated either by the ordinary 
complement of serum or by lecithin. Hence, we 



ACTION OF SALTS. 161 

have here an instance of the entire cytolytic action 
being performed by two known chemicals, which 
in their action appear to be analogous to ambocep- 
tors and complements. Yet even the action of 
these substances is obscure, for although the chem- 
ical formulae of silicic acid and lecithin are suffi- 
ciently well known, the explanation of their activ- 
ity as colloids is equally obscure with that of the 
albuminous substances. 

Another recent discovery which tends to bring Neutralization 
the immune substances into closer touch with pure Cy Sa7ts. ement 
chemistry is that of Hektoen concerning the abil- 
ity of certain salts (calcium chlorid, barium 
chlorid, etc.), to combine with complement in 
such a way that the latter loses its activating and 
combining function in relation to amboceptors. 
This was mentioned incidentally under the sub- 
ject of antitoxins. The activity of the comple- 
ment is again restored if the inhibiting salts are 
precipitated by suitable chemicals. The salts are 
used in such dilutions that they are largely ionized, 
and Manwaring believes their inhibiting action is 
due to the formation of compounds of the posi- 
tive ions with the complement, resulting in such 
substances as Ca-complement, Ba-complement, 
etc. When the precipitating chemicals are added 
the ions are freed from this combination, as a re- 
sult of which the complement recovers its activat- 
ing properties. It has not as yet been determined 
whether variations in the salts in the fluids of the 
body cause changes in resistance by their action on 
native complements. 



CHAPTER XIII. 



Cytotoxin or 

Cytolysin. 



Theoretical 

Utility of 

Cytotoxins. 



CYTOTOXICS. 

Following the discovery of immune hemolytic 
serums it was a short step to experiments which 
involved immunization with various other tissue 
cells, and as a result of such work we are to-day 
familiar with antiserums for almost every organ 
of the body. 

Metchnikoff gave the name of cytotoxins to those 
serums which destroy cells other than bacteria 
and erythrocytes; the word cytolysin is used syn- 
onymously. Naturally a serum which destroys any 
cell whatsoever is cytotoxic, but according to the 
rather loose custom which prevails, we speak of 
bacteriolysins, hemolysins and other cytolysins, in- 
cluding among the latter serums which destroy 
leucocytes, the cells of the liver, kidney and other 
organs. 

Cytotoxins are of interest, not only because they 
are produced in accordance with the general 
laws of anti-body formation, but they have, in ad- 
dition, a certain theoretical and perhaps practical 
importance. Immediately on their discovery the 
possibility became manifest that they might be 
utilized in the elucidation of certain physiologic 
and pathologic problems. For example, by put- 
ting the thyroid out of function through in- 
jections of thyrotoxic serum it might be pos- 
sible to confirm, or to prove incorrect, cer- 
tain theories as to the role of the gland in 
metabolism. Or, by the selective destruction of a 
tissue, facts concerning its regenerative powers 



SPECIFICITY. 1G3 

might be learned. The use of an antipancreatic 
serum might throw some light on the nature of 
diabetes. Therapeutic possibilities also suggested 
themselves. One might be able by means of artifi- 
cial anticytotoxic serums to counteract cytotoxins 
which were being formed pathologically in the 
body. Or, by injecting small amounts of a exo- 
toxin, perhaps one could stimulate to a renewed 
production of the homologous cells ; small doses of 
a hemolytic serum might be useful in combating 
anemias. Or small amounts of leucotoxic serum 
might cause an increase in the number of leuco- 
cytes, and thereby an increased resistance to infec- 
tion. Perhaps auto'cytotoxins are formed in some 
such manner as the following: An extraneous 
toxic substance causes the * destruction of a few 
kidney cells, the constituents of the latter reach 
the circulation and stimulate other organs to the 
formation of autonephrotoxic amboceptors, which 
then assist in the destruction of more renal tissue, 
with the result that a vicious cycle is set up. 

In spite of so many theoretical values, the study Lack of 
of cytotoxic serums has not yielded the results Specif,c,ty - 
which were anticipated, perhaps chiefly because of 
their lack of specificity (Pearce and others). Al- 
though the cells of the different organs differ wide- 
ly in their morphology and function, there are no 
doubt certain chemical constituents (receptors) 
which they possess in common. Of this we have 
experimental proof from the fact that immuniza- 
tion with one type of cell yields a serum which is 
toxic for the colls of various organs. It is difficult 
or impossible to injure one organ to the exclusion 
of all others by means of a cytotoxin. One may 
attempt to purify a cytotoxic serum through ab- 



J64 



INFECTION AND IMMUNITY. 



Determination 

of Cytotoxic 

Action. 



Technic of 
Immunization. 



sorption of the adventitious amboceptors by means 
of the corresponding cells. Inasmuch, however, as 
the result is a decrease in the chief amboceptors 
as well as of the adventitious, the desired object is 
not fully realized. Theoretically the cytotoxic 
treatment of malignant tumors offers an impor- 
tant field for research. But here, too, various dif- 
ficulties are involved, as lack of specificity of 
serums and the multiplicity of cell-types which 
constitute different tumors. 

Experiments with cytotoxic serums may be con- 
ducted in vitro or in the living animal. In either 
case a necessary condition for the recognition of 
the cytotoxic action is the presence of some dis- 
tinctive sign of vitality on the part of the cell, the 
loss of which may be taken as evidence of cell- 
death. Loss of motility and of proliferative power 
indicate the death of bacteria, and solution of 
hemoglobin the death of erythrocytes. Under par- 
ticular conditions loss of motility on the part of 
certain tissue cells, as spermatozoa, leucocytes and 
ciliated epithelium, is an evidence of cell death or 
cell injury. The toxic action of serums on cells of 
fixed form is more difficult to determine, and for 
evidence one must rely on such points as clearing 
of the protoplasm (digestion?), swelling of the 
cell and nucleus, actual solution of the cytoplasm, 
or degenerations of the homologous organs when 
the serum is injected into the living animal. 

The technic of immunization with tissue cells is 
similar to that of immunization with bacteria. In 
order to obtain leucocytes in abundance, artificial 
leucocytosis is produced in the peritoneal or pleural 
cavity by the injection of bouillon, or lymph 



AMBOCEPTORS AXD COMPLEMENTS. 165 



glands, spleen or bone-marrow may be ground up 
and injected. 

Immunization with solid organs, as liver, kidney 
or testicle, is easily accomplished, a necessary pre- 
liminary for injection being a thorough disintegra- 
tion of the tissue by grinding with sterile sand; 
the resulting mass when suspended in salt solution 
passes through the injecting needle readily. 

Cytotoxins, like bacteriolysins and hemolysins, 
are complex substances, in that they consist of am- 
boceptors and complements. The amboceptors 
alone are increased during immunization, the com- 
plement being a normal constituent of the serum 
of the animal. The phenomena of inactivation 
and reactivation are observable here as in connec- 
tion with other cytolytic serums. Anticytotoxins 
are readily produced by immunization with many 
cvtotoxins ; the antiserum usually consists of anti- 
complement, but in some instances antiambocep- 
tors have been described. 

Simultaneously, or nearly so, Landsteiner in 
Vienna and Metchnikoff in Paris reported the 
production of spermotoxic serums by immuniza- 
tion with spermatozoa, the natural motility of 
which rendered the recognition of cell death easy. 
The technic which Landsteiner first employed was 
that of the Pfeiifer experiment in that he immun- 
ized guinea-pigs with the spermatozoa of cattle and 
observed loss of motility on the part of the cells 
when they were injected into the peritoneal cavity 
of the immunized animals. Comparable with 
many other cytotoxins, spermotoxin kills the ho- 
mologous cell without causing its solution. The 
loss of motility is also observer! in hanging-drop 



Amboceptors, 
Complements 
and Anticyto- 
toxins. 



Spermotoxin. 



preparations provided a fresh 



complemented 



166 INFECTION AND IMMUNITY. 

serum is used. Most normal serums show a 
greater or less degree of toxic action for the sper- 
matozoa of other animals, and normal spermotox- 
ins like the immune consist of amboceptor and 
complement. Metchnikoff claims to have pro- 
duced an autospermotoxin by immunizing guinea- 
pigs with the spermatozoa of other guinea-pigs. 

When a spermotoxic serum is injected into the 
living animal it is thought that the amboceptors 
are taken up by the homologous cells, and this 
would seem to affect the vitality of the sperma- 
tozoa, inasmuch as De Leslie rendered male mice 
sterile for 16 to 20 days by the injection of the 
serum. 

It is of theoretical interest that castrated ani- 
mals will yield spermotoxin by immunization, 
showing that the amboceptors are not of necessity 
produced by the analogous ti-ssue of the immun- 
ized animal. From the fact that spermotoxic 
serums are hemolytic, it is assumed that certain 
receptors are common to erythrocytes and sperma- 
tozoa. Hemolytic serums, on the other hand, may 
not be spermotoxic. There is nothing contradic- 
tory in this lack of reciprocal action, for those re- 
ceptors which are common to the two cells may not 
be important for the life of the spermatozoon, 
whereas the opposite condition prevails with the 
erythrocyte. 

It is certainly of interest that immunization with 
the plasma of ova causes the formation of spermo- 
toxic amboceptors, a fact which points to certain 
common constituents of the two cells. 

Antispermotoxin may be produced by immuniza- 
tion with spermotoxic serum ( ant i complement or 
antiamboceptor). 



LEUCOTOXIC SERUM. 167 

Following technic similar to that employed by Cytotoxin 
Landsteiner, von Dungern obtained a ototoxic Epithelium. 
serum for ciliated epithelium of the trachea. The 
cells disintegrated in the peritoneal cavity of the 
immunized animal, but not in that of the normal 
animal. This serum also proved to be hemolytic 
in spite of the fact that no erythrocytes were in- 
cluded in the injections. That the receptors which 
characterize ciliated epithelium are widely distrib- 
uted is shown by the fact that immunization with 
cow's milk causes the formation of a cytolytic 
serum for the tracheal epithelium of the cow. 

Leucotoxic, lymphotoxic or lymph at otoxic Leucotoxin. 
serums are prepared by immunization with ex- 
udates which are rich in leucocytes, or with the 
emulsions of lymphoid organs: lymph glands, 
spleen, bone marrow. Metchnikoff prepared the 
first serum of this nature by the injection of the 
spleen of rats into guinea-pigs. Leucotoxic serums 
are toxic, not only for leucocytes, but also for red 
corpuscles and endothelial cells. When injected 
into the peritoneal cavity the endothelium is 
thrown off, and when given subcutaneously the 
capillary endothelium is attacked, with the result 
that blood escapes to form a large hematoma. The 
action of the serum on leucocytes may be observed 
in vitro. The mononuclear cell's are often more 
susceptible than the polymorphonuclears, although 
this depends somewhat on the animals and the 
particular organ used for immunization. The cells 
lose their motility, the cytoplasm becomes trans- 
parent, and swells to form a large clear vesicle, 
which appears to be surrounded by a sharp, thin 
membrane. The cell contents may be discharged 
or entirely liquefied, the nucleus alone being rec- 



168 



INFECTION AND IMMUNITY. 



Old Age. 



Effect of Leu- 
cotoxic Serum 
on Resistance 
to Infections. 



ognizable. Leucocytes are agglutinated by the 
serum. A strong leucotoxic serum may be fatal 
to the animal when injected into the peritoneal 
cavity or blood stream, the exact cause of death 
being obscure. 

Metchnikoff, taking the view that the phenom- 
ena of old age depend on the* destruction of vari- 
ous tissue cells by the mononuclear leucocytes 
(macrophages), expressed the hope that a lympho- 
toxic serum might be utilized to combat the action 
of these cells with the result that life would be 
prolonged. Whether or not his view as to the 
cause of old age is correct, his plan of antagonizing 
it had to be abandoned because leucotoxic serums 
do not injure the macrophages to the exclusion of 
other leucocytes. 

The injection of a leucotoxic serum into the per- 
itoneal cavity of a guinea-pig causes a temporary 
decrease in the number of leucocytes, and during 
this period of hypoleucocytosis the resistance of the 
animal to peritoneal infections with the organisms 
of typhoid and cholera is lowered. One may refer 
this effect to the destructive action of the serum 
on the leucocytes, by which phagocytosis is pre- 
vented, or, according to Wassermann, it may de- 
pend on the action of anticomplement which the 
leucotoxic serum contains. (Leucocytes contain 
complement, hence immunization with leucocytes 
causes the formation of anticomplement.) It is 
probable that both factors are of influence. In the 
course of 24 to 48 hours after peritoneal injection 
of the serum, the leucocytes reaccumulate to an 
enormous extent. During this secondary hyper- 
leucocytosis resistance to peritoneal cholera or 
typhoid is increasecl. Some non-toxic substances, 



NEPHROTOXIC AND NEPHRITIS. 169 

as bouillon, have a similar effect, and although the 
secondary leukocytosis is never so great as that 
caused by the leucotoxic serum, the protective ac- 
tion is equally high. It would seem that, leucocyte 
for leucocyte, those which accumulate following 
the injection of leucocytoxic serum are less efficient 
in antibacterial action than those whose presence 
is caused by nontoxic substances. (Eicketts.) 
Hence there probably is no field for leucotoxic 
serum as a means of temporarily increasing resist- 
ance* to bacterial infections. 

By guarded immunization Besredka obtained an 
antileucotoxic serum. 

Nephrotoxic serums have been brought into Nephrotoxic 
close relationship with clinical and anatomic prob- Serum - 
lems by a number of investigators. Some normal 
serums are held to be nephrotoxic inasmuch as 
their injection is followed by albuminuria and 
renal degenerations. Immune nephrotoxins have 
a similar but more pronounced effect, and Linde- 
man referred the death of his experiment animals 
to the development of a uremic condition. Of 
more than ordinary interest is the claim of cer- 
tain workers that autonephrotoxins may be formed 
in the body. One (Lindeman) caused a toxic 
nephritis in dogs by the injection of potassium- Autenephro- 
bichromate. The serum of this dog, although free 
from chromic acid, was toxic for other dogs, pro- 
ducing the symptoms which are caused by an im- 
mune nephrotoxic serum. It was supposed that 
the chromic acid in the nYst dog caused disintegra- 
tion of renal cells and that the constituents of the 
latter 'were then taken up by nephrotoxic receptors 
which normally reside in the organs of the ani- 
mal ; as a result the receptors were overproduced 



170 INFECTION AND IMMUNITY. 

and their presence became manifest when the 
serum was injected into other dogs. In accord- 
ance with this view the original toxic cause of a 
degenerative nephritis would be of less conse- 
quence for the continuance of the condition than 
the formation of the nephrotoxic amboceptors ; i. e., 
the formation of an autonephrotoxin. 

Somewhat similar results were obtained by oth- 
ers through ligation of the renal vein or artery on 
one side. Constituents of cells of the isolated kid- 
ney were supposed to be absorbed, and as a conse- 
quence nephrotoxic amboceptors were produced in 
excess by organs of uncertain identity. To the 
action of the new-formed bodies were attributed 
the degenerative changes which were found in the 
opposite kidney, and the nephrotoxic properties 
which the serum manifeested when injected into a 
healthy animal of the same species. 
Antinephro- According to Ascoli and Figari unilateral neph- 

toxin, Cardiac , . . ., ., -. . ■, , , x 

Hypertrophy, rectomy so injures the opposite kidney (overwork) 
that the serum of the animal becomes nephrotoxic. 
They state also that an animal, the serum of which 
contains nephrotoxin, may antagonize the latter 
by the production of antinephrotoxin, and suggest 
that spontaneous recovery from nephritis may be 
due to the action of such an antibody. They would 
account for the cardiac hypertrophy of nephritis 
by the action of nephrotoxic serum in causing con- 
traction of the peripheral vessels with consequent 
increase of blood pressure ; and for the nervous 
symptoms on the basis that the serum contains a 
neurotoxic constituent. 

We hardly dare consider such far-reaching con- 
clusions as decisive until they have been extensively 
confirmed. Yet whatever may be their real value 



HEPATO- AXD NEUROTOXINS. 



171 



they serve to emphasize the possibility that those 
principles which are so important in relation to 
immunity against infectious diseases, may be 
equally important in relation to other pathologic 
conditions. 

Hepatotoxins have been obtained by a number Hepatotoxins 
of workers, and the attempt has been made to pro- 
duce autohepatotoxins by injecting liver tissue of 
the guinea-pig into animals of the same species. 
The success was not unqualified. Hepatotoxins 
when injected are reported to cause insular degen- 
erations of the liver ; however, the lesions may be 
caused, in part at least, by capillary emboli of en- 
dothelial cells or erythrocytes. 

Xeurotoxic serums have been studied with some Neurotoxin. 
thoroughness. Whether one injects the cerebrum, 
cerebellum or spinal cord, the resulting serums 
apparently are similar; either an anticerebral or 
an anticerebellar serum will cause degenerations 
of the spinal ganglion cells. In view of their 
broad range of action it seems improbable that 
neurotoxic serums will be of service in clearing up 
the etiology of system degenerations of the nervou's 
tracts. They are usually hemolytic and hemag- 
glutinating and may also be endotheliotoxic and 
leucotoxic. When mixed with emulsions of the 
homologous brain tissue the neurotoxic ambocep- 
tors are bound by the receptors of the nervous tis- 
sue, and the serum consequently loses its toxicity. 
Antiueurotoxic serums have been described. 

Syncytiolysin is the name given to a serum which 
is obtained by immunization with the placenta. 
Certain writers (Yeit and Scholten, Charrin and 
Belamare) report that the injection of placentar 
tissue alone causes albuminuria, a consideration 



Cyncytiotoxin 
in Relation to 
Eclampsia. 



172 INFECTION AND IMMUNITY. 

which led them to assume that the placentar cells 
contain a nephrotoxic substance. Inasmuch as 
placentar cells or their constituents may reach the 
circulation during eclampsia (Schmorl) it was 
not a long step to suppose that the nephritis of 
pregnancy is due to the toxic syncytial cells which 
are absorbed. The results which Weichardt re- 
ported gave some strength to the view just cited. 
By treating placentar tissue of rabbits with the 
specific cyncytiolysin the toxin supposedly was lib- 
erated, and the mass when injected into normal 
rabbits is said to have produced symptoms of an 
eclamptic nature. On the basis of these observa- 
tions the hope has been expressed that an anti- 
toxin for eclampsia might be prepared by immun- 
ization with placentar tissue. However, the con- 
ditions are by no means simple; any value which 
the destruction of circulating syncytial cells or 
their toxin would afford might be more than offset 
by the action of the hemotoxin and neurotoxin 
which the serum is said to contain. Whether or 
not the hypothetical toxin of syncytial cells may 
be separated from the other cell constituents, and 
whether immunization with the toxin will yield 
an antitoxic serum are possibilities which remain 
for further investigation ; the results cited have 
not been obtained by all observers. 

Liepmann hopes for a serum-diagnosis of preg- 
nancy. If, as supposed, the blood of a pregnant 
woman contains syncitial cells or their products 
of degeneration, the serum when mixed with 
a specific syncytiolysin may cause a precipitate. 
He claims to have demonstrated the presence of 
placentar constituents in the circulation by this 
biologic method. 



THYRO-, PAXCREOTOXIX, ETC. 



173 



Sympathetic 
Ophthalmia. 



Antithyroid serum is prepared by immuniza- Thyrotoxic 
tion with ground-up thyroid tissue or with extracts 
of the organ. It is hemolytic, even though all the 
blood has been washed from the tissue which was 
injected. Portis immunized with the "colloid" 
material of the gland obtaining a hemolytic thyro- 
toxic serum. When injected into the living animal 
degenerative changes are produced in the thyroid, 
and some authors report the tetanic phenomena 
which often follow surgical removal of the thyroid. 
In very careful work, however, Portis could not 
produce "the exact picture presented by thyrodec- 
tomized animals." Degenerative changes were 
found in various organs, as liver, spleen and kid- 
neys. 

Brown Pusey has made the interesting sugges- 
tion in regard to s}Tnpathetic ophthalmia that the 
disease may be due to the formation of autocyto- 
toxins which are specific for the cells of the inner 
surface of the ciliary body and iris. The disinte- 
gration products of the corresponding cells in the 
eye which was primarily injured would constitute 
the stimulus to the formation of the specific anti- 
bodies. The possibility is as yet a problematic 
one. 

The experimental study of cytotoxic serums for 
the pancreas has, up to the present time, thrown 
little light on pancreatic diseases. It stated that 
the serum may cause transient glycosuria, and it 
is said to have an antitrvptic action in experiments 
performed in the test -glass. 

The results of different observers concerning the 
action of antiserums for the adrenal gland are not 
in entire accord. Although degenerative changes 
mav be caused in the gland when the serum is in- 



Pancreotoxin. 



Other 
Cytotoxins. 



174 



INFECTION AND IMMUNITY. 



Toxin of 
Exhaustion. 



Concerning 
Autocytotoxins. 



Autotoxicus. 



jected, the action is not specific; the serum may 
be highly hemolytic (Abbott). 

Ceni claims to have demonstrated in the circula- 
tion of epileptics a cytotoxin which causes the ep- 
ileptic attacks, and reports the production of a 
specific antitoxin. 

Weichardt has published descriptions of a toxin 
which is peculiar to states of exhaustion, giving 
an account of the specific antitoxin which he pro- 
duced by immunization. 

Other cytotoxins which have been prepared, as 
those for the pituitary body, gastric mucosa and 
cardiac muscle, have at the present time nothing 
more than general biological interest. 

It would seem that no question in relation to 
cytotoxic serums is more important than the pos- 
sibility that autocytotoxins may develop and in- 
stitute the vicious cycle which was mentioned ear- 
lier. It is true that the results of some investiga- 
tors suggest the probability of such a process, but 
it would be going too far to say that its existence 
as an important pathologic law has been estab- 
lished. On the contrary, the development of auto- 
cytotoxins is one of the rarest of occurrences in 
experimental work; and Ehrlich has spoken of 
the inability of the body to form such antibodies 
Horror as a condition of "horror autotoxicus/' The cells 
of our kidneys and our erythrocvtes certainly do 
degenerate, and it is quite possible that the recep- 
tors which are thereby liberated "actually reach 
cytotoxic amboceptors which are situated in other 
organs. In the event that the process extends to 
this point, Ehrlich assumes that the amboceptors 
are of a sessile nature, that in spite of the stimula- 
tion to which the cells are subjected the "sessile 



"HORROR AUTOTOXINS." 175 

amboceptors" may not be overproduced and lib- 
erated as in the case of antibodies for bacterial 
substances or for the cells of other species. In 
accordance with this explanation we are saved 
from intoxications of the nature in question be- 
cause of the sessile nature of the cytotoxic ambo- 
ceptors. 



CHAPTEE XIV. 



PHAGOCYTOSIS. 

As one may learn from the writings of Metchni- 
koff, phagocytosis, in its broad sense, exercises 
three distinct functions: nutritional, resorptive 
and protective. 
Phagocytosis Phagocytosis, for purposes of nutrition, is most 
ofNutStion! highly developed in unicellular ameboid organ- 
isms, but is found also in animals of considerable 
organic differentiation. It is, perhaps, nowhere 
more striking than among certain myxomycetes, 
which are large, naked, multinucleated, protoplas- 
mic masses belonging to the plant kingdom, and 
which possess a peculiar, slow, undulating motility. 
Ingestion is accomplished through protoplasmic 
arms (pseudopodia) which are thrown out to en- 
velop the object. Minute plant and animal cells, 
living or dead, are ingested in this manner by the 
myxomycetes, amebse and other unicellular organ- 
isms and are subsequently digested by means of 
intracellular ferments. The ferments which have 
been extracted from such cells are proteolytic since 
they digest gelatin and fibrin, usually in an acid 
but sometimes in an alkaline medium; that from 
ameba? has been called amibodiastase. In the proc- 
ess of digestion a "vacuole," acid in reaction and 
containing the ferment, forms around the in- 
gested particle. In certain phagocytic unicellular 
organisms the protoplasm shows a degree of differ- 
entiation, a mouth and an anus being simulated at 
points where the food is most readily taken in and 
discharged. Instances are cited in which ameboid 



Phagocytes. 



CHEMOTAXIS. 177 

organisms protect themselves against inimical cells 
by ingesting, killing/ and finally discharging or 
digesting the latter. 

The botanist, Pfeiffer, first described the phe- chemotaxis. 
nomena of negative and positive chemotaxis in re- 
lation to the myxomycetes. Under certain condi- 
tions they either are attracted toward or move 
from moist places. That a negative chemotaxis 
may be changed into a positive was shown in rela- 
tion to salt solutions. When placed in the vicinity 
of or in contact with strong solutions the cell re- 
cedes, whereas if one passes gradually from weaker 
to stronger solutions the latter eventually attract 
rather than repel the cell. 

As one goes higher in the animal scale intracel- jntestinai 
lular digestion for purposes of nutrition is con- 
fined to rather definite groups of cells. The intes- 
tinal epithelium of certain invertebrates consists 
of "sessile phagocytes/' cells which, individually 
or after fusion into plasmodial masses, surround 
and digest solid particles of food. It is said that 
in sponges the digestive tract is not sharply sepa- 
rated from the mesodermal tissue, and the cells of 
the latter share with the former the function of 
intracellular digestion. 

In higher invertebrates and in all vertebrates 
the intestinal epithelium ceases to be essential! v 
phagocytic, digestion being accomplished rather by 
ferments which have been secreted by the intestinal 
and related glandular epithelium. Such animals, 
nevertheless, possess an abundance of phagocytic 
cells, but they are in the main mesoblastic in na- 
ture, and may have nothing more than a remote 
relationship to the nutrition of the organism. 



178 INFECTION AND IMMUNITY. 

Macrophages Metchnikoff divides the phagocytic cells of ver- 

and Micro- . . n f -■ . i 

phages, tebrates into the macrophages and the micro- 
phages. The macrophages or large phagocytes in- 
clude the large lymphocytes, endothelial cells, 
ameboid connective tissue cells and others which 
may occasionally take up foreign particles. Our 
polymorphonuclear leucocytes are the macro- 
phages. In relation to immunity we are concerned 
chiefly with the large lymphocytes (macrophages) , 
and the polymorphonuclear leucocytes (miero- 
phages). Although such cells may contain many 
ferments, Metchnikoff recognizes but one type in 
Cytases. relation to their resorptive, digestive and bacteri- 
cidal activities. This he calls cytase and distin- 
guishes that of the macrophage as macrocytase and 
that of the microphage as microcytase. Cytase 
corresponds to the complement of Ehrlich. The 
two cells do not have identical activities, the ma- 
crophage being concerned specially in the resorp- 
tion of tissue cells and in immunity to certain 
chronic diseases, as tuberculosis and leprosy, 
whereas the microphage is the cell which is con- 
spicuously antimicrobic in relation to acute infec- 
tions. 
Resorption of According to Metchnikoff, the leucocytes are 
very active in the resorption of useless or foreign 
cells. During the metamorphosis of certain in- 
vertebrates it is said that the larval tissues are 
englobed and digested by wandering pha- 
gocytic cells. In involution of the uterus 
the muscular tissue is invaded by leuco- 
cytes which take up and digest or carry away the 
"retrogressive elements." MetchnikorFs concep- 
tion of certain atrophic processes, particularly 



Native Cells. 



ATROPHIC PROCESSES. 



179 



those which are grouped among the senile atro- 
phies, is of interest to pathologists. In sclerotic 
atrophy of the ovaries the large lymphocytes in- 
vade the tissue, surround and destroy the ova and 
follicular epithelium and eventually, as fibroblasts, 
participate in the formation of fibrous tissue which 
to a degree is substituted for the original struc- 
ture. In old individuals or in those of failing 
mentality it is said that ganglionic cells are found 
in a greater or less degree of atrophy because of 
the action of certain mononuclear phagocytes 
( neuronophagies) which are contiguous to or form 
a zone around the cell. The neuronophages may 
represent mononuclear cells from the blood or 
those of proliferated neurogliar tissue. The best 
examples of this condition were found in very old 
dogs. The chromophores of the skin, according to The whitening 
Metchnikoff, may be considered as chromophages. 
Whether or not they are of epithelial origin, as he 
claims, they are said to exist normally in the hairs 
in a latent or inactive condition. As old age comes 
on, or as a result of other obscure causes, their 
attitude becomes an active one, and they proceed 
to take up and digest the normal pigments of the 
hairs. Hence, white hairs are the result of an 
antoparasitism by certain mononuclear phago- 
cytes. In muscular atrophy it is held that the 
sarcoplasm takes up the striated tissue after the 
manner of phagocytes. 

We come into closer touch with our general sub- Resorption of 
ject of immunity when we consider the resorptive Fore '9 n Ceils. 
function of the phagocytes for cells which are for- 
eign to the host, for example, toward erythrocytes 
which are injected for the purpose of producing a 



180 INFECTION AND IMMUNITY. 

hemolytic serum. Following such an injection into 
the peritoneal cavity there occurs a great accession 
of macrophages which ingest the erythrocytes, dis- 
solve the hemoglobin arid eventually digest the 
stroma. The same phagocytes are involved in the 
resorption of any other foreign cells of animal ori- 
gin which may be injected. In view of the intracel- 
lular hemolysis by the leucocytes, one may suspect 
that the latter contain a hemolytic ferment; one 
F< Cytotox?ns! which, perhaps, is analogous to the hemolysin 
(hemolytic amboceptors and complement) of 
serums. On this point there has been sharp dis- 
cussion. Metchnikoff cites observations to show 
that a ferment of this nature may be extracted 
from the lymphoid organs, that it contains a heat- 
susceptible constituent, and that when fresh it 
may be used to reactivate a heated hemolytic 
serum. This would indicate that the leucocytes 
contain cytase (complement), but it is not clear 
that they would also contain the fixators (ambo- 
ceptors). Nevertheless, the demonstration of an 
intraleucocytic hemolysin and a knowledge of the 
phagocytic power of the leucocytes for erythro- 
cytes form the basis for MetchnikofPs belief that 
serum-hemolysin is nothing more than intraleuco- 
cytic hemolysin, which under proper conditions 
may reach the serum or plasma. By an extension 
of this conception it is held that all cytolysins are 
produced by the macrophages. 
Thermostabiie Korschun and Morgenroth, on the other hand, 
0riTa O n ly E S x"r!cts! obtained from lymphoid and various other organs, 
not a thermolabile hemolysin, but one which with- 
stands prolonged boiling — a coctostabile hemolysin 
which is soluble in alcohol, shows no amboceptor- 



CYTASE. 181 

complement composition, and is incapable of yield- 
ing antihemolysin by immunization. These re- 
sults, Metchnikon 2 holds, are only in apparent dis- 
cord with those obtained b} r himself and his pu- 
pils, and depend on the methods of extraction 
which were employed. In order to obtain the ther- 
molabile hemolysin uncontaminated with the ther- 
mostabile, the extraction must be a rapid one. If, 
on the other hand, it is prolonged, as Metchnikoff 
assumes that of Korschun and Morgenroth to have 
been, the intracellular ferments digest the remain- 
ing cell constituents, including the thermolabile 
hemolysin, and the thermostabile hemolysin is lib- 
erated or formed in the process. 

Believing that cytase, under normal conditions, 
exists only within the leucocytes, and that its pres- 
ence outside these cells is artificial, Metchnikoff 
cites experiments similar to the following in sup- 
port of his views : 

Given a guinea-pig which has been immunized cytasean 
with the blood of a goose : if fresh goose corpuscles substance^ 
are injected into the peritoneal cavity, the cells are 
hemolyzed in the fluid without the occurrence of 
phagocytosis. Two explanations of the extraleu- 
cocytic presence of cytase and fixators, which is in- 
dicated by this result, are possible: first, that they 
are present normally and continuously in the plas- 
ma of the immunized animal, or, second, that they 
become liberated at the time the corpuscles are in- 
jected. According to MotehnikofT, the latter conten- 
tion prevails rather than the former. He recognizes Phagoiysis. 
a phenomena which bears the name of phagolysis, 
i. e., solution, partial or complete, or phagocytes. 
Almost any foreign substance or fluid which one 



182 INFECTION AND IMMUNITY. 

Liberation of may choose to put in contact with leucocytes so 
Pbagoiysis^ stimulates or injures them that they discharge cer- 
tain of their constituents. If the fixators and 
cytase are among the constituents which are dis- 
charged at the time the injection is made, the 
extracellular hemolysis encountered in the experi- 
ment described above might depend on the libera- 
tion of these substances rather than on their nat- 

Preventionof ural occurrence in the plasma. If this be true, 
and if one could in some way fortify the leucocytes 
against phagolysis, the plasma would remain free 
from hemolytic power. Metchnikoff accomplishes 
such fortification, i. e., prevents phagolysis," by a 
simple procedure, which demands nothing more 
than the peritoneal injection of a small quantity 
of bouillon or salt solution twenty-four hours in 
advance of the experiment. Possibly by this 
means the leucocytes have been habituated to the 
presence of a foreign fluid, or the new leucocytes 
which accumulate possess greater resistance. What- 
ever the explanation, the erythrocytes which are 
injected at this critical time are said not to un- 
dergo extracellular hemolysis, but instead are en- 
globed and dissolved by the macrophages. These 
results and others of a similar nature are the basis 
for the belief that cytase normally is intracellular, 
and that it becomes extracellular only when the 
leucocytes are subjected to injurious influences. 
The fact that the serum of defibrinated or coagu- 
lated blood contains cytase is not in discord with 
such an opinion, for in this instance also the leu- 
cocytes may be injured to such a degree that cer- 
tain of their constituents are discharged. We are 
well aware that fibrin-ferment is liberated under 
these circumstances. 



NATURAL IMMUNITY. 183 

It was equally desirable, if possible, to determine Fixators 
the relation of fixators to the leucocytes. The sit- Leucocytes* 
uation is, however, very complex, and, although 
Metchnikoff regards the fixators as secretion or ex- 
cretion products of phagocytic cells, the question 
is, perhaps, not definitely settled. When phagoly- 
sis is prevented in the manner described, the in- 
jected erythrocytes may well absorb fixators from 
the plasma and still undergo no hemolysis until en- 
globed by the phagocytes. It is considered that 
fixators in contrast to cytase may exist in the cir- 
culating plasma. 

Phagocytosis as a feature of local resistance phagocytosis 
against microbic invasion was considered in rela- mlmmun,t y- 
tion to inflammation. We come now to speak of 
the relationship of the leucocytes to general 
states of immunity, having reference to the condi- 
tions which have been designated as natural and 
acquired antibacterial immunity, and natural arid 
acquired antitoxic immunity. 

The first expressions of Metchnikoff concerning 
the antimicrobic activity of phagocytes, the power 
of freeing the organism from "invaders of every 
sort," were made altogether from an a priori stand- 
point in an address delivered in 1883, "Ueber die 
Heilkriifte des Organismus." He justified his po- 
sition on general grounds, having in mind the 
"more general phenomena of phagocytosis and the 
resorption of corpuscular elements," as he had 
observed them in various zoological studies. 

Shortly there came to him the opportunity of Natural immun- 
etudying an infectious disease among the Daplmia ,vto 
(water-flea), a small transparent crustacean. The 
disease was caused by a blastomycee which forms 



184 INFECTION AND IMMUNITY. 

a long needle-shaped spore. After being swal- 
lowed by the animal the spores penetrate the in- 
testinal wall into the body cavity where they are 
surrounded, englobed and digested by the white 
blood corpuscles. If this occurred with sufficient 
vigor all the spores were disposed of and the ani- 
mal recovered. Sometimes, however, the spores 
germinated even after they had become intracellu- 
lar, and when the parasitic cells reached maturity 
they apparently had the power of killing the leu- 
cocytes through the agency of a secretion peculiar 
to themselves. In the event that the latter proc- 
ess was sufficiently extensive the tissues were soon 
overrun with parasites and death resulted from a 
septicemic condition. The observations were made 
in the living transparent animal. 

Although the example cited seemed convincing, 
Natural it was, of course, necessary that observations 
should extend over many infectious processes be- 
fore phagocytosis as the cause of natural immunity 
could be accepted as a general fact. This has been 
done on rather broad lines by Metchnikoff and his 
pupils, and the results have served to convince 
them that the phagocytes are responsible for nat- 
ural immunity in all instances, and that the de- 
gree of natural immunity in a given case depends 
on the degree of phagocytosis which is manifested 
against the organism. As stated previously, the 
microphage, with its microcytase, is held responsi- 
ble for antibacterial immunity in most instances, 
although the macrophage is concerned in certain 
chronic infections. 

If an animal is susceptible to a virulent culture 
of anthrax, but resistant to a weak culture, the 



TOXINS AND CHEMOTAXIS. 



185 



phagocytic power is found to be greater for the 
weaker organism. The highly virulent culture 
creates a condition of negative chemotaxis, with 
the consequence that leucocytes are not attracted 
and microbic proliferation proceeds rapidly. 
Without going into details, studies of the follow- 
ing and perhaps other micro-organisms have 
strengthened Metchnikoff in his views: staphylo- 
cocci, streptococcus, pneumococcus, gonococcus, 
vibrio of cholera in infections of the guinea-pig, 
the vibrio of goose septicemia in relation to the 
guinea-pig, which is naturally immune, the spi- 
rillum of relapsing fever, tubercle bacillus, yeast 
cells and other fungi, and certain animal para- 
sites (Trypanosoma lewisii) , 

Most important are certain conditions which 
create a condition of negative chemotaxis, or other- 
wise engage the phagocytes so that they refuse to 
take up the essential organism. Vaillard says 
that all animals are immune to pure cultures of 
the tetanus bacillus or its spores, provided the lat- 
ter have been washed entirely free of toxin. The 
absence of toxin permits of positive chemotaxis 
and phagocytosis, whereas toxin when present 
causes negative chemotaxis, and the bacilli pro- 
ceed to further toxin formation. The same is held 
to be true in" infections by some other organisms. 

It seems definitely established that contaminat- 
ing organisms (pyogenic cocci, Bacillus prodicjio- 
sus) may greatly increase the virulence of the ba- 
cillus of symptomatic anthrax, Bacillus aerogenes 
capsulatus and the tetanus bacillus — anaerobic or- 
ganisms. On the one .hand, the secondary bac- 
teria may produce more favorable conditions for 



Relation of 
Phagocytosis 
to Virulence 
of Bacteria. 



Toxins as Cause 
of Negative 
Chemotaxis. 



Accidental 
Engagement 
of Phagocytes. 



186 INFECTION AND IMMUNITY. 

the growth of the anaerobes by consuming local 
oxygen, or, as Metchnikoff believes, they may so 
engage the phagocytes that the latter have no dis- 
position to take up the essential organism. This 
condition may be an important one in other mixed 
infections, as when the streptococcus complicates 
diphtheria and scarlet fever. 

Acquired If the phagocytic power is an index of the de- 
to bacteria! gree of natural antibacterial immunity, is the same 
correspondence to be recognized when the immun- 
ity is acquired ? To answer this question satisfac- 
torily it is necessary to bring phagocytosis in rela- 
tion to two different types of antibacterial immun- 
ity which it is possible to recognize. Cholera is an 
example of that type of antibacterial immunity in 
which the bactericidal power of the serum under- 
goes a great increase. It is stated that anthrax 
represents another type in which the immunity is 
not dependent on the bactericidal power of the 
serum. Probably the same may be said of acquired 
immunity to the streptococcus, staphylococcus and 
the pneumococcus, yet it is perhaps not definitely 
established that the immunity in these instances 
is antibacterial rather than antitoxic. For the 
present we may, however, with Metchnikoff, con- 
sider that the immunity is antibacterial and that 
it is a cellular or phagocytic immunity. 

Anthrax. Babbits which have been immunized against 
anthrax respond to subcutaneous or intraperitoneal 
injection of a virulent culture by concentrating so 
vast a number of microphages at the site of inocu- 
lation that the fluid becomes purulent in appear- 
ance. Examination shows an enormous degree of 
phagocytosis. When, on the other hand, non-im- 



IX FLU EX CE OF SERUM. 



187 



mime rabbits are submitted to similar inocula- 
tions, the fluid which accumulates locally is of a 
clear serous character, contains few leucocytes, and 
no phagocytosis is observable ; the animals die of a 
rapidly developing septicemia. From the results 
one may well suspect that the immunity is related 
to and perhaps coextensive with the acquired pha- 
gocytic power. 

But is the serum of no influence? It has often 
been held that phagocvtes take up bacteria only 
after the latter have been injured or killed by the 
serum or plasma. Metchnikoff answers this objec- 
tion experimentally by inoculating an immune rab- 
bit with anthrax, withdrawing some of the exu- 
date at a time when phagocytosis is complete, and 
injecting it into a non-immune rabbit. The sec- 
ond animal dies. Since none but phagoevtized 
bacilli were injected into the non-immune rabbit 
( ! ) , and since the latter succumbs to anthrax, it 
seems not only unnecessary, but unjustifiable, to 
assume that the bacteria must be attenuated by 
the serum before they can be taken up by the leu- 
cocytes. May the serum, nevertheless, have some 
obscure action which may not be included under 
such terms as bactericidal and attenuating? It 
seems fairly well established that anti-anthrax 
serum, at least from certain animals, may exert a 
protective influence when injected into other ani- 
mals in conjunction with or in advance of the cul- 
ture; yet Metchnikoff discredits the importance of 
such protection and says that "those properties of 
the body fluids, as the bactericidal, preventive and 
agglutinating, fall away into the background in 
such examples of immunity." It is the tendency 



Phagocytes 
Take Up 
Virulent 
Bacteria. 



The Influence 
of 



188 INFECTION AND IMMUNITY. 

of the school of Metchnikoff to refer the protective 
power of a serum to its faculty of stimulating the 
phagocytes rather than to its effect on the micro- 
organisms. We shall see, however, in speaking of 
opsonins (p. 193) that even in relation to anthrax 
the serum may possess a distinct property which 
facilitates phagocytosis, not by stimulating the 
phagocytes but by some action on the bacteria. 
cholera and Concerning those diseases in which immunity 
Sl fect1onsi is characterized by a great increase of the bac- 
tericidal amboceptors or fixators, Metchnikoff does 
not disregard the existence or importance of the 
immune bodies, but rather seeks to show that they 
are a product of phagocytic activity. The con- 
ditions are held to be similar to those already 
mentioned in connection with intra vitam hemoly- 
sis. That is to say, microcytase exists only in the 
leucocytes of the immune animal under normal 
conditions ; it escapes into the plasma, or into the 
serum during coagulation, only as a consequeuce 
of the phagolysis already mentioned. The phe- 
nomenon of Pfeiffer occurs only because the in- 
jected culture injures the leucocytes, resulting in 
the liberation of microcytase, which in conjunction 
with the fixators causes the solution of the vibrio. 
When phagolysis is prevented by a preceding in- 
jection of bouillon, phagocytosis and intracellular 
solution of the organisms entirely supplant extra- 
cellular solution. 
intravascular If an immune animal receives an intravascular 
and Phagolysis! injection of the vibrio of cholera and is sacrificed 
shortly, the relation of the organisms to the leu- 
cocytes may be studied in stained microscopic sec- 
tions of the organs (lungs). Leucocytes which 



FORMATION OF GYTASE. 189 

have undergone phagolysis are seen to be clumped 
in the pulmonary vessels and in their immediate 
vicinity one finds many micro-organisms which 
have been changed into the characteristic granules 
by the action of the cytase which has escaped from 
adjacent leucocytes. Coincident with the phe- 
nomenon of phagolysis, the leucocytes lose their 
phagocytic power; hence, no bacteria are found 
within the leucocytes. On the other hand, all 
those vibrios which are remote from the leuco- 
cytes have a perfectly normal appearance. Phago- 
lysis in the blood stream may be prevented, just as 
in the peritoneal cavity, by a preceding injection 
of bouillon into the vessels. In this instance when 
the culture is injected no extracellular solution or 
transformation of the organisms into granules 
takes place, but as in the peritoneal cavity, their 
destruction is accomplished entirely within the 
microphages. Metchnikoff holds to the correct- 
ness of these observations and interpretations, al- 
though contradictory results were obtained by 
Pfeiffer and his pupils. As further evidence that Mkrocytase is 
cytase does not exist normally in the plasma Metch- |ntracel,u,ar - 
nikoff cites the condition which is found in the 
anterior chamber of the eye in immune animals. 
The vibrios continue unaffected in the aqueous 
humor until such a time as leucocytes wander in, 
when they are destroyed by phagocytosis. Hence, 
cytase does not exist in the aqueous humor, and 
if not in the aqueous humor it is surely absent 
from the plasma; for if present in the plasma it 
would reach the anterior chamber by a process of 
diffusion. Similar conditions prevail in edematous 
fluids. In another instance a portion of a vein, 



190 INFECTION AND IMMUNITY. 

filled with blood, was resected and centrifugated 
without the formation of a clot (absence of pha- 
golysis) ; the plasma contained no cytase. Also 
G-engou collected and centrifugated blood in tubes 
which were coated with paraffin, and thus avoided 
clotting; here also cytase was absent from the 
plasma. 
increase of It would seem, then, that two important anti- 
of 'phagocyte bacterial factors characterize immunity to cholera 
Power. an( ^ S j m -Q ar infections : the development of specific 
fixators, and a greatly increased phagocytic power 
on the part of the leucocytes. Metchnikoff leans 
to the view that bacteria, having absorbed fixators, 
are more readily phagocytized, but no clear idea is 
given as to the change which the fixators produce. 
However, he would not refer the increased phago- 
cytic power entirely to the influence of the fixa- 
tors. He believes that the leucocytes of the im- 
mune animal have per se a higher phagocytic 
power than that of the normal animal. In anthrax, 
for example, the phagocytic power is height- 
ened in spite of the fact that there is no increase 
in specific fixators. This view, however, is op- 
posed by Denys and Leclef, who found that the 
leucocytes of the immune animal, when trans- 
ferred to normal serum, had no greater phago- 
cytic power than normal leucocytes. 
Fixators Metchnikoff believes that fixators, like cytase. 
Macrophage! are produced by the microphage. That the lymph- 
oid organs may form certain fixators seems prob- 
able from the observations of Pfeiffer and Marx 
in regard to cholera and Wassermann and Takaki 
in typhoid. During the process of immunization 
and at a time when amboceptors were absent from 



AXTITOXIC IMMUXITY. 



191 



the serum they could be demonstrated in the blood- 
forming organs (spleen, lymph glands, bone-mar- 
row). Metchnikoff suggests that they may be pro- 
duced in these organs by the microphages which 
have wandered in after having englobed the micro- 
organisms. In contrast to cytase the fixators read- 
ily abandon the leucocytes which produced them 
and become a constituent of the plasma. 

The leucocytes have also been brought in rela- Natural 
tionship to antitoxic immunity and the formation [o Toxins. 
of antitoxins. In experimental tetanus exudates 
which are rich in leucocytes contain more toxin 
than does a similar quantity of blood. That is to 
say. the leucocytes have the power of absorbing 
toxins, and it is held that the natural immunity 
of the animal depends on the degree to which this 
power is present. The immunity of the chicken 
to tetanus depends not on non-susceptible nerve 
cells nor on the presence of natural antitoxin, but 
on the absorbing power of the leucocytes for the 
toxin. Xot only do leucocytes absorb toxins, but 
it is held that they also are the producers of anti- 
toxins. As compared with the side-chain theory, 
it is a peculiarity of the view of Metchnikoff that 
antitoxin does not represent a constituent of the 
tissuo cells, but rather the toxin itself, which has 
been altered by leucocytic activity in a manner as 
yet obscure. 

In passive antitoxic immunity the idea of a Passive 
chemical union between toxin and antitoxin does 
not meet with general acceptance among the up- 
holders of the phagocytic theory. It is sometimes 
said that antitoxins are ehVaeions from the fact 
that they stimulate phagocytosis (absorption) of 



Antitoxic 
Immunity. 



192 INFECTION AND IMMUNITY. 

the toxin, the latter then suffering disintegration 
in the leucocytes. 
Summary. The following statements summarize the phago- 
cytic theory of immunity as conceived by Metch- 
nikoff : 

1. Natural immunity to bacteria depends on 
and is coextensive with phagocytosis and subse- 
quent digestion of the microbes. Intraleucocytic 
destruction of the micro-organisms is accomplished 
by the cytase, possibly aided by intraleucocytic fix- 
ators. Normal serum is devoid of both fixators 
and cytase. 

2. Acquired immunity to bacteria depends on 
the establishment of a heightened phagocytic power 
as the result of immunization or infection. In 
diseases like anthrax, in which fixators are not in- 
creased, this new power is an acquired property 
of the leucocytes and is independent of any in- 
fluence on the part of the serum. In diseases like 
cholera, the new fixators which are formed may 
render the micro-organisms more susceptible to 
phagocytosis, but this is probably secondary to 
increased, function on the part of the phagocytes. 
Both cytase and fixator are produced by the pha- 
gocytic cells. In acquired active immunity to 
bacteria the fixators may be free in the serum 
and plasma, but the cytase is intracellular. In all 
cases cytase becomes extracellular only as the re- 
sult of phagolysis. 

3. In passive immunity to bacteria, as when an 
antibacterial serum is injected for the sake of 
prophylaxis or cure, the serum is efficacious chiefly 
because it stimulates the leucocytes to increased 
phagocytosis. 



SUMMARY; OPSOXINS. 193 

4. Xatural immunity to toxins depends on the 
power of the leucocytes, and perhaps the genera- 
tive organs, to absorb the toxin. 

5. Active immunity to toxins is established 
through the activity of the leucocytes, by which 
the toxin is probably so changed as to constitute 
antitoxin. 

6. In passive antitoxic immunity the antitoxin 
presumably acts by stimulating the phagocytes to 
an increased absorption of the toxin. 

Many investigators are earning on work in re- opsonins. 
gard to phagocytosis and the properties of serums 
from a point of view which is entirely unbiased. 
From sources of this nature discoveries of recent 
date indicate that phagocytosis of micro-organisms 
by the leucocytes is impossible without the aid of 
some property in the serum. It seems that these 
substances, which the discoverers, Wright and 
Douglas, call opsonins, act directly on the bacteria, 
and that there is no reason to suppose that their 
virtue lies in a stimulation of the phagocytes them- 
selves. The facts which permit of this deduction 
are the following : 1. When the fresh defibrinated 
blood of some animal is mixed with the culture of 
a suitable micro-organism (staphylococcus, strep- 
tococcus, anthrax bacillus, etc.) and placed in the 
thermostat for 20 or 30 minutes, stained prepara- 
tions of the mixture show that the polymorphonu- 
clear leucocytes contain a large number of the mi- 
crobes. 2. If, however, all the serum is washed 
from the blood before adding the micro-organisms, 
practically no bacteria are ingested. This shows 
the importance of the serum, but does not differ- 
entiate between some effect on the leucocytes, on 



194 INFECTION AND IMMUNITY. 

the one hand, or the bacteria, on the other. 3. 
In order to decide this point one may subject the 
suspension of bacteria to the action of fresh cell- 
free serum, and after a contact of about 30 min- 
utes remove all the serum by centrifugation, and 
mix the "sensitized" culture with serum-free 
blood; phagocytosis occurs almost to the same de- 
gree as when the fresh defibrinated blood, contain- 
ing serum, is used. These results seem to show 
definitely that phagocytosis depends on the power 
of the opsonins to affect the bacteria in some pe- 
culiar manner. Opsonins are very susceptible to 
heat, and, like complement, disappear spontane- 
ously from the serum in a short time. Hektoen 
and Euediger, and Bulloch and Atkin have con- 
firmed the observations of Wright and Douglas 
and the former have added facts of importance. 
It seems that opsonin has a structure like that of 
toxin, i. e., a haptophorous and an opsoniferous 
group; "by heating sensitized bacteria the opson- 
iferous group appears to be destroyed, but the in- 
active opsonin (opsonoid) by saturating the re- 
ceptors of the bacteria prevents further sensitiza- 
tion by fresh serum" (Hektoen and Euediger). 
Various salt solutions neutralize the opsonins. 
Opsonins will be brought into still more important 
relationship to phagocytosis if it can be shown 
'definitely that they are increased as the result of 
immunization or infection. 



CHAPTEE XV. 



THE SIDE-CHAIN THEORY OF EHRLICH AND ITS 

RELATION TO THE THEORY OF 

PHAGOCYTOSIS. 

In 1885, before the discovery of toxins and anti- 
toxins and before there was any knowledge as to 
the real nature of immunity, Ehrlich 1 published a 
small volume on the "Oxygen Eequirements of the 
Body." Herein the belief was expressed that the 
assimilation of foods by cells is accomplished only 
after chemical union has taken place between the 
food substance and some constituent of cellular 
protoplasm. It is not the understanding that as- 
similation is at an end, however, when this union 
has occurred, for certain molecules of complex 
chemical nature and of great size must be split up 
into simpler substances before they can enter into 
the composition of protoplasm. Therefore, the cell 
constituent which combines with the nutritious 
molecule serves only as a link to bring the food- 
stuff into relation with the digestive, oxidizing or 
fermentative activities of the cell. 

Ehrlich speais of that portion of living proto- 
plasm which represents the cellular activities as 
the "Leistungsliern" of the cell, the center of cel- 
lular activity, or the central group of the proto- 
plasm, whereas those chemical groups which bind 
the food substances are called the side-chains of the 
" Li istungskern." 

The author of the theory has made his concep- 



Side-Chain 
Theory Ap- 
plied to 
Nutrition. 



"Leistungs- 
kern" and 
Side-Chains. 



1. Ueber das Sauerstoffbedurfnis des Organismus. 



196 INFECTION AND IMMUNITY. 

tion more tangible through an analogy which was 
drawn with the so-called ring or nucleus of benzol 
and its side-chains. The molecule of benzol, C 6 H 6 , 
has a definite formation in which each carbon 
atom is linked to two others in such a manner as 
to form a ring; three valences of each carbon 
atom are satisfied in this way, and the fourth is 
satisfied by atoms of hydrogen, one of which is at- 
tached to each carbon atom, thus : 

H 

I 

C 

/ * 
H-C C-H 

H-C C-H 

x II 

C 

A 

This ring is analogous to the "Leistungskern" of 
the cell. A great variety of chemical compounds 
exists and very many may be produced syntheti- 
cally by substituting for one or more atoms of 
hydrogen, one or more other groups of atoms which 
may be very simple or very complex. The groups 
which have been substituted are called side-chains. 
Thus benzoic acid is formed from benzol by sub- 
stituting the acid radical CO OH for a particular 
H, and the CO OH in this instance is a side-chain 
of the ring : 

o 
c 

I^OH 
C 
/ * 

H-C C-H 

II I 

H-C C-H 

x // 

C 



SIDE-CHAIXS. 197 

Just as the side-chains of the "LeistungsTcern" 
may combine with food particles, so may the side- 
chains of the benzol ring combine with other 
groups of atoms and thereby assimilate the latter, 
so to say, into the ring. To choose a simple exam- 
ple, the sodium of sodium hydroxid may unite with 
the side-chain CO OH to form sodium benzoate, 
the hydrogen of the acid radical being replaced by 
the sodium, thus: 

o 
c 

I^O-Na 
C 
/ * 
H-C C-H 

II 
H-C C-H 

N. // 

c 



Presumably it is in some such manner as sodium 
is brought into relationship with the benzol nu- 
cleus, in the example cited, that the food sub- 
stances are brought into relationship with the 
"Leistungskern" of the cell. 

The hypothesis of Ehrlich carries with it the Haptophores. 
assumption that the side-chains of a cell possess or 
consist of definite groups of atoms capable of unit- 
ing chemically with certain other definite groups 
of atoms in the food particles ; hence both the side- 
chain and the food substance have combining 
groups — haptophores. The side-chains of the cells 
Ehrlich now calls receptors, elements which we 
have already recognized in connection with im- 
munity. Inasmuch as different foods have differ- 
ent chemical compositions, it is likely that their 
binding groups are not identical; and if this be 



1/ 



198 INFECTION AND IMMUNITY. 

true there must exist marry kinds of receptors each 
of which is able to unite only with that food sub- 
stance which has a corresponding binding group of 
atoms. 

In contrast to the condition with respect to 
foods, it is held that chemical substances of known 
composition, drugs and alkaloids never become in- 
corporated as a part of the protoplasm, that is, 
they do not unite with cell receptors, although 
they may affect the vitality and function of proto- 
plasm profoundly.. Their inability to yield anti- 
bodies as a result of immunization is supposed to 
depend on this condition. Such substances, ac- 
cording to Ehrlich, exist in the cell in a condition 
of unstable salt formation with some constituent 
of the protoplasm, or in a state of solid solution. 

The following statement from a recent publica- 
tion by Ehrlich summarizes the' nutritional aspect 
of the theory : ,"We must assume that all sub- 
stances which enter into the structure of proto- 
plasm are fixed chemically by the protoplasm. We 
have always distinguished between assimilable sub- 
stances which serve for nutrition and which enter 
into permanent union with the protoplasm, and 
those which are foreign to the body. No one be- 
lieves that quinin and similar substances are as- 
similated, that is, enter into the composition of the 
protoplasm. On the other hand, the food sub- 
stances are bound in the cells, and this union must 
be considered as chemical. One can not extract a 
sugar residuum from cells with water, but must 
first split it off with acids in order to set it free. 
But now such a chemical union, like every syn- 
thesis, demands the presence of two binding 



APPLICATION TO IMMUNITY. 199 

groups of maximal chemical affinity, which are 
suited one to the other. The binding groups which 
reside in the cells and which bind food substances 
I designate as side-chains or receptors, while I 
have called those of the molecules of foodstuffs the 
haptophorous groups. I also assume that proto- 
plasm is endowed with a large series of such side- 
chains, which through their chemical constitution 
are able to bind the different foodstuffs and there- 
by provide the prerequisite for cellular metabol- 
ism." 

If the side-chain theory of nutrition is to be- side-Chain 
come the side-chain theory of immunity it is nee- plied to 
essary that it undergo elaboration in order that the mmum v * 
formation of antibodies may be adequately ex- 
plained. If, as Ehrlich assumes, the union of 
toxin with cell receptors causes the overproduction 
of the latter as antitoxin, and if this union is an- 
alagous to that of food substances with similar re- 
ceptors, one may wonder that antibodies are not 
formed for our ordinary foods, antibodies which 
would be discharged from the cells and which 
would unite with circulating nutritious particles 
and thereby bring about a condition of starvation. 
Without entering into the intricacies of this ques- 
tion, it seems probable that normally a condition 
of physiologic equilibrium exists between the food 
substances on the one hand and the cellular activi- 
ties on the other, so that the union of food with 
protoplasm constitutes no abnormal stimulus to 
the "Leistungshern" of the cell. When, however, ' 
cells are diverted from their normal metabolic 
function by union witli toxins and other "abnormal 
food substance?." the effect on the eel] is de- 



200 INFECTION AND IMMUNITY. 

scribed as a cell defect, the defect consisting of the 
functional elimination of the receptor. The "Leis- 
tungshem" as the vital or regulating center of the 
cell repairs the defect by the formation of new re- 
. ceptors, and in harmony with the hypothesis of 
Weigert produces not only enough to repair the 
defect, but a great excess, with the result that 
many are thrown into the circulation. The anal- 
ogy of the "Leistungskern" with the benzol ring 
ean not be carried to this extent, for the latter has 
no power of reproducing side-chains to take the 
place of one which has been bound by some new 
group of atoms. 
Essential It will be appropriate in this place to consider 
Enriich's the character of the proof which has been offered 
eory * in support of the three tenets which constitute the 
framework of the theory of Ehrlich. These three 
tenets may be expressed as follows: 1. Antitox- 
ins counteract toxins by entering into chemical 
union with them; a similar union takes place be- 
tween other antibodies and their homologous sub- 
stances. 2. Toxins in injuring cells combine 
chemically with a definite constituent of the proto- 
plasm, the cell receptor; other antigenous sub- 
stances 2 enter into similar union with the appro- 
priate receptors of cells. 3. The specific antibodies 
of the serum are new-formed receptors identical in 
structure with those which, as cell constituents, 
had combined with the homologous' antigens. 
Chemical union First tenet : In the early days of studies on im- 
with Antigens, munity (1890-1897), the action of a toxin and the 
efficacy of an antitoxin could be determined only 

2. An antigen or an antigenous substance is one which 
is able to cause the formation of an antibody. 



TOXIN AND ANTITOXIN. 201 

by injecting these substances into living animals, 
and the animal experiment naturally continues to 
be the means of testing the curative and prophy- 
lactic values of serums. So long, however, as such 
experiments were performed exclusively in the liv- 
ing animal the nature of the action of antitoxin 
remained to a certain extent in doubt. It re- 
mained uncertain whether antitoxin is protective 
because it actually destroys the toxin, because neu- 
tralization of a chemical nature occurs, or because 
in some manner it increases the resistance of the 
inoculated animal. In Chapter viii, p. 78, experi- 
ments were cited to show that antitoxin does not 
destroy the toxin, and this is generally admitted to- 
day. There continues to be some difference of opin- 
ion, however, in relation to the two other possibili- 
ties, i. e., as to whether antitoxin combines chemi- 
cally with toxin, or is efficacious because of its 
stimulating power on the tissues of the animal. 
Behring, the discoverer of antitoxin, was from the 
beginning an exponent of the chemical theory, even 
at a time when the conceptions of Ehrlich had not 
been fully developed. On the other hand, certain 
noted investigators, especially Eoux and Buchner, 
and later MetchnikofT, stood for the alternative 
view. 

Following closely on Behring's great discovery, Ricin and 
Ehrlich studied the nonagglutinating toxin ricin, 
from the castor-oil bean, and by immunization 
with it produced a specific antitoxin, i. e., anti- 
ricin. Eicin is toxic to erythrocytes both in the 
animal body and in the test-tube, and if it could 
be shown that antiricin protects in the test-tube 
by a direct effect on the toxin, it was highly prob- 



Antiricin. 



202 INFECTION AND IMMUNITY. 

able that its action in the animal body would be of 
a similar nature. The results left no doubt in the 
mind of Ehrlich that antiricin unites chemically 
with ricin, and the applicability of this principle 
in animal experiments became all the more ap- 
parent when it was shown that the proportion of 
antiricin which protects in vitro also protects in 
oivo. It is held that similar proof of chemical union 
between bacterial hemolysins, the hemolysin of 
venom and the leucocidin of the staphylococcus 
with their respective antitoxins is- equally valid. 
chemicaiNature Although the animal body can riot be dispensed 
zatlonofifSs with in testing the action of the antitoxins of 
by Antitoxins, diphtheria and tetanus, certain principles of chem- 
ical action are found to prevail which leave no 
doubt in regard to the chemical neutralization of 
the toxins. If neutralizing proportions of diph- 
theria toxin and antitoxin be mixed in a test-tube 
and injected immediately, the serum does not af- 
ford absolute protection; if, however, the mixture 
is allowed to stand for from fifteen to twenty min- 
utes before injection, the protection is absolute. 
This alone would point to an action of the anti- 
toxin on the toxin, for the completion of which a 
certain amount of time is required. For the com- 
plete neutralization of tetanus toxin by its anti- 
toxin about forty minutes are necessary at ordinary 
temperatures. Then certain other chemical princi- 
ples described in Chapter viii, p. 79, are found to 
hold true: That neutralization proceeds more 
rapidly at higher than at lower temperatures, more 
rapidly in concentrated than in dilute solutions, 
and that it takes place in accordance with the law 
of multiple proportions. 



AMBOCEPTORS, ETC. 203 

Granting, then, that neutralization of toxin by 
antitoxin is of a chemical nature, the first essential 
step in the chemical or side-chain theory is estab- 
lished. If antitoxin combines chemically with 
toxin, union must occur through combining groups 
which each molecule possesses. Herein lies the ex- 
perimental justification for assuming the existence 
of haptophorous groups. 

The situation is more difficult in regard to the Union of Aggiu- 
union of receptors of the second and third orders, ceptors with 
i. e., agglutinins and amboceptors with the ho- 
mologous receptors of bacteria and other cells. 
One can not titrate bacteria against agglutinin or 
bactericidal amboceptors so exactly as toxin can be 
titrated against antitoxin, for, in the first place, 
it is difficult to obtain at will a desired concentra- 
tion of bacteria, and to keep it without alteration, 
and, in the second place, bacterial cells contain 
many more receptors than are necessary for their 
agglutination and solution. A given mass of bac- 
teria will take up varying quantities of agglutinin, 
depending on the concentration of the latter, and 
the same principle applies to the absorption of 
bactericidal and hemolytic amboceptors. As more 
and more agglutinin is added, the total amount 
absorbed increases with each addition, although 
the ratio of absorbed to un absorbed agglutinin 
grows less continuously. The conditions which 
govern this phenomenon are not understood. 
Perhaps no condition speaks more decisively for 
chemical union of these bodies with cell receptors 
than immunization experiments which were car- 
ried on with colls which had been treated with a 
great excess of the specific antiserum. The as- 



204 INFECTION AND IMMUNITY. 

sumption was made that if one could force all the 
receptors of erythrocytes, for example, to take up 
the specific amboceptors, such corpuscles should 
lose their power to cause the formation of a hemo- 
lytic serum when injected into a suitable animal. 
This would follow logically, for the receptors of 
the corpuscles, being already bound, would not be 
free to unite with receptors of the immunized ani- 
mal. Antibodies were not formed under these cir- 
cumstances, from which it is concluded that the 
receptors of the erythrocytes had united chemi- 
cally with the antibodies of the serum (Sachs). 
In order to completely occupy all the receptors of 
the vibrio of cholera Pferffer used 3,000,000 to 
4,000,000 times the dissolving amount of the anti- 
cholera serum. Although the mere absorption of 
agglutinins and amboceptors by the homologous 
cells is cited in favor of the chemical hypothesis, 
we may bear in mind the contention of certain in- 
vestigators that this absorption is physical rather 
than chemical. 
ChemicaiNature Second tenet : What evidence have we that tox- 
?ns Ln and°Crther ^ ns aiL( ^ °^ ner antigenous substances enter into 
Antigens with chemical union with receptors in the cells of the 

Cell Receptors. . . * 

immunized animal? It is probable that no ob- 
servation speaks more strongly in favor of such 
union than a famous experiment of Wassermann's 
in which the central nervous system of guinea- 
pigs was ground up with tetanus toxin, the mix- 
ture allowed to stand for a short time and then 
injected into mice. The mixture was found to be 
non-toxic, and further experiments showed that 
the neutralizing power resides in the solid tissue 
in the emulsion. It is claimed by Ehrlich that 



UNION WITH CELLS. 205 

this experiment demonstrates positively that 
chemical union of tetanus toxin takes place with 
constituents of the nervous tissue. The toxin hav- 
ing been completely neutralized can not again be 
extracted from the tissue. The condition is the 
opposite in relation to some poisonous alkaloids, 
as strychnin, which it appears does not combine 
with the protoplasm firmly and may again be ex- 
tracted by simple methods. 

Von Dungern conducted very important work 
with the precipitins, which is interpreted as show- 
ing that albuminous substances other than toxins 
are taken up chemically by the cells. He injected 
considerable quantities of a foreign serum into the 
veins of rabbits and studied its disappearance from 
the blood of the injected animal. Traces of the 
foreign serum could be recognized by treating the 
rabbit serum with a specific precipitin for the for- 
mer, the precipitin having been obtained pre- 
viously by the immunization of other animals. 
The foreign serum disappeared from the circula- 
tion of the rabbit with some rapidity and since it 
could not be demonstrated in the excretions, it 
seemed necessary to assume that it had been bound 
by the cells, that is to say, by the cell receptors. 

Third tenet: Is there any direct experimental Proliferation 
proof that those constituents of cells which have of Receptors - 
been designated as cell receptors actually undergo 
multiplication in the cell itself as a preliminary to 
their discharge into the circulation in the form of 
antibodies? If this condition could be demon- 
strated in one instance, one might reasonably con- 
sider that it typifies a law according to which all 
antibodies are formed. Further experiments by 



206 INFECTION AND IMMUNITY. 

von Dungern with the precipitins seem to show 
that snch intracellular overproduction actually 
does occur. The experiments concern the fate of 
"Majaplasma" (plasma of the crawfish) when in- 
jected into the circulation of the rahhit (see 
above). If a single injection of the serum is 
given, a specific precipitin for the latter body in 
due time may be demonstrated in the serum of the 
rabbit. Eventually the precipitin disappears from 
the circulation by excretion or other means. At 
that time, when all the precipitin has disappeared, 
one may assume that the cells of the animal still 
contain an increased number of precipitin recep- 
tors, although the latter are no longer produced to 
such an extent that they are thrown into the cir- 
culation. If this condition exists the tissues of 
the animal at this time should be able to absorb a 
, larger amount of the foreign serum, given in a sec- 
ond injection, and perhaps absorb it more rapidly 
than the tissues of an untreated rabbit. Using a 
specific precipitating serum in order to detect 
traces of the foreign serum which still remained in 
the blood of the injected animal, von Dungern de- 
termined that its tissues actually do absorb the 
plasma more rapidly than do the tissues of the 
untreated rabbit. The cells of the former have a 
greater absorbing power, i. e., a greater binding 
power for the plasma; therefore, an increased 
number of receptors. 

These examples are, perhaps, sufficient to illus- 
trate the principles of experimentation which have 
been followed in the attempt to obtain definite 
proof of the correctness of the essential points of 
the theory. The results are in entire accord with 



OTHER TENETS. 207 

the primary assumptions and show that the theory 
continues to serve as an explanatory basis for 
newly-discovered facts, and as a foundation on 
which new researches may be instituted. 

In addition to the three main principles treated other import- 
of above, the following points are necessarily in- SF Ehriich , . ples 
eluded in a summary of the views of Ehrlich, many 
facts of a corroborative nature having been ascer- 
tained in independent laboratories. 

1. The recognition of different types of tissue 
receptors by which peculiarities in the action of the 
different antibodies are explained. Eeceptors of 
the first order, as antitoxins, anticomplements and 
antiamboceptors, are regarded as relatively simple 
bodies because no other constituent can be recog- 
nized than the haptophorous group by which they 
combine with their homologous substances. Ee- 
ceptors of the second order are more complicated 
in that they have something more than the mere 
binding power; usually they are able to produce 
some observable change in the substance with 
which they unite. Hence, each has a toxophorous 
or a zymotoxic group in addition to the hapto- 
phorous, and the two groups are part of the same 
molecule. Toxins, agglutinins, precipitins and 
complements are receptors of the second order. 
Receptors of the third order, i. e., the bacterio- 
lytic, hemolytic and cytotoxic amboceptors, are 
still more complex in that they are, so to say, only 
partial antibodies, the complete body consisting of 
the amboceptor-complement complex. The ambo- 
ceptor is not an active body, but serves as an in- 
termediary body to connect the active substance, 
complement, with the cell. In the cytolytic proc- 



208 INFECTION AND IMMUNITY. 

ess the amboceptor through its cytophilous hapto- 
phore first unites with the cell, and as a result 
acquires an increased affinity for complement, 
with which it unites through its complemento- 
philous haptophore. Only after this double union 
is completed may complement affect the cell. 
From this it follows that complement in the cyto- 
lytic process does not combine with the cell di- 
rectly. As previously stated, Bordet and others 
oppose the idea that the absorption of these bodies 
is of a chemical nature, considering it rather to be 
a physical process. 

Ehrlich has intimated his belief that tissue am- 
boceptors play the chief role in the fixation of 
foods by the cells of the body. 

2. The chemical theory explains the specificity 
which characterizes the formation and action of 
antibodies. Every antigen has a haptophore which 
is different from those of other antigens; conse- 
quently, it unites only with the corresponding cell 
receptor, and the latter when overproduced and 
cast into the circulation retains its specific binding 
power for the corresponding antigen. 

3. The multitude of antibodies which have been 
obtained indicate that the cells contain a vast 
number of different receptors which correspond to 
the three types now recognized ; that is, there is a 
different antitoxin receptor for every kind of 
toxin, etc. 

4. Ehrlich has limited the application of the 
term toxin to those substances of animal or plant 
origin, immunization with which causes the forma- 
tion of specific antitoxins. Other characteristics 
have been given in Chapter vii, p. 65. 



COMPLEXITY OF TOXIXS. 209 



5. Keceptors of the second order, toxins 
tinins, precipitins and complements, undergo a 
peculiar degenerative change, spontaneously or as 
a result of exposure to injurious agents, in which 
the toxophorous or zymotoxic group disappears or 
is rendered inactive. The termination -oid is af- 
fixed to the altered bodies, as toxoid, agglutinoid, 
precipitoid and complementoid. Wechsberg has 
described a similar degeneration of one of the hap- 
tophores of amboceptors, calling the product am- 
boceptoid. Toxoids and complementoids on im- 
munization cause the formation of corresponding 
antitoxins and antic omplements, by virtue of re- 
tention of their haptophorous groups. 

6. By means of a special technic devised for 
studying the neutralization of toxin by antitoxin, 
i. e., the partial saturation method, Ehrlich found 
diphtheria toxin to be a very complex substance. 
Not all the molecules of the toxin have the same 
affinity for antitoxin, and according to the de- 
grees of their affinity have received the names of 
prototoxin, deuterotoxin and tritotoxin. Simi- 
larly, protoxoids and syntoxoids are molecules of 
toxoid having different affinities for antitoxin. 
These conditions are represented graphically by 
means of the "toxin spectrum" described pre- 
viously. 

7. Ehrlich claims that the diphtheria bacillus 
secretes two toxins, one of which causes the acute 
manifestations of diphtheritic intoxication, where- 
as the second toxin, i. e., toxon, has a prolonged 
incubation period and probably causes diphtheritic 
paralysis. Toxon has a lower affinity for diph- 
theria antitoxin than the other constituents of the 



210 INFECTION AND IMMUNITY. 

toxin solution, but is neutralized by the same anti- 
toxin. This view is strongly opposed by Arrhe- 
nius and Madsen, who, working on the basis that 
the neutralization of toxin takes place according 
to certain laws of physical chemistry, claim that 
toxon is nothing more than toxin which has disso- 
ciated from the toxin-antitoxin molecule. 

8. It is thought that the incubation period 
which characterizes the action of toxins represents 
to a large degree the time required for the action 
of the toxophorous group after the toxin has been 
bound by the cells. 

9. Ehrlich stands for the multiplicity of com- 
plements in opposition to Bordet and others who 
claim the existence of but one complement 
(alexin). The various complements differ in the 
nature of their haptophores, without regard to 
possible differences in their zymotoxic groups. 

10. Only those organs which have suitable re- 
ceptors may produce an antibody for a given anti- 
gen, i. e., only those cells which may enter into 
chemical combination with the antigen. It does 
not follow, however, that only those organs which 
shew clinical or anatomic lesions may produce, 
say, an antitoxin; for other organs not so suscep- 
tible to the action of the toxin may still possess 
the suitable receptors and cast them out as anti- 
toxin. 

Causes of Dif- The various types of immunity are explainable 
on the basis of the side-chain theory in the follow- 
ing terms: 

1. Natural immunity to toxins may depend on 
(a) a lack of suitable cell receptors, the toxin con- 
sequently finding no point of attack; (b) a very 



ferent Types 
of Immunity. 



TYPES OF IMMUNITY. 211 

low affinity between cell receptors and toxin so 
that the latter does not nnite with the cells except 
under special conditions (e. g., the immunity of 
chicken to tetanus) ; or (c) on the presence of 
natural antitoxins. 

2. Acquired active antitoxic immunity depends 
on the multiplication and excretion of cell recep- 
tors (antitoxin) into the circulation, the new- 
formed bodies having the power of combining 
chemically with additional toxin which may be in- 
troduced. 

3. Passive antitoxic immunity, as established by 
the injection of an antitoxin, depends on the abil- 
ity of the antitoxin to combine chemically with the 
toxin and thus to divert the latter from the cells. 

4. Natural immunity to bacteria depends on (a) 
a lack of suitable cell receptors with which the 
toxic bacterial constituents might combine; (&) a 
very low affinity between cell receptors and the 
toxic bacterial constituents; or (c) on the presence 
of natural bacteriolysins (amboceptors and com- 
plements). 

5. Acquired active antibacterial immunity de- 
pends on the multiplication and excretion into the 
circulation of specific cell receptors (amboceptors) 
which have the power of uniting with complement 
to kill the micro-organisms which may be intro- 
duced. 

6. Passive antibacterial immunity, as estab- 
lished by the injection of a bacteriolytic serum, 
depends on the ability of the amboceptors con- 
tained in the serum to unite chemically with the 
receptors of the micro-organism, as a result of 
which complement is absorbed to kill and perhaps 



Metchnikoff. 



212 INFECTION AND IMMUNITY. 

to dissolve the bacteria. The complement may be 
present in the serum which is injected, or the nat- 
ural complement of the individual may be utilized 
by the amboceptors. 
Comparison of When one seeks to compare the theory of Ehrlich 
Ehr°ich%n<i with that of Metchnikoff, one finds little more in 
common than the general purpose of explaining 
the phenomena of immunity. Yet it is remark- 
able that where there is so little in common there 
are so few contradictions of an essential nature. 

The theory of Ehrlich has that degree of defi- 
niteness which it must have in order to be a plausi- 
ble chemical theory, whereas that of Metchnikoff 
seems more general in that it is so largely biologic 
and vitalistic. 

Each has a certain relation to nutrition. Phago- 
cytosis as a nutritional measure is found in lower 
types of animals, and accomplishes nothing further 
than to bring the food substance in contact with 
the digestive ferments contained in the cell. In 
relation to nutrition the theory of Ehrlich begins, 
so to say, where the phagocytic theory leaves off, 
involving, as it does, the method by which food 
substances become a part of the protoplasm. 

Metchnikoff, with Ehrlich, recognizes the vari- 
ous antibodies which have been discovered. The 
former holds that all are produced by the phago- 
cytes without suggesting clearly a method by 
which they may be formed. Ehrlich assumes a 
very precise method by which they may be formed, 
but designates no particular cells as their pro- 
ducers, stating only in a general way that an anti- 
body is produced only by those cells with which the 



EHBLICH AND METCHNIKOFF. 213 

antigen may combine; in some instances, the leu- 
cocytes may be such cells. 

The theory of Metchnikoff is not concerned with 
the structure of toxins and the various antibodies, 
nor with the method by which toxins may injure 
the ceils, whereas Ehrlich presents definite concep- 
tions on these points. 

Both recognize that there is more than one com- 
plement (cytase). Ehrlich recognizes no limit to 
the varieties which may exist, whereas Metchnikoff 
describes but two cytases, microcytase and macro- 
cytase. 

The view which Metchnikoff has expressed, that 
antitoxin is produced by some action of the phago- 
cytes on the toxin, is directly opposed to that of 
Ehrlich which recognizes antitoxin as a product of 
the cell itself. 

They agree that amboceptors (fixators) become 
extracellular in the blood. 

Metchnikoff holds that complements (cytases) 
are produced only by the phagocytes and that 
these substances are found in the plasma or serum 
only as a result of injury to the phagocytes (phago- 
lysis). These points are not involved essentially 
in the theory of Ehrlich. Certain investigators 
who work in harmony with the side-chain theory, 
as well as those who represent the views of Metch- 
nikoff, have extracted complement from the leuco- 
cytes. Some of Ehrlichias supporters believe that 
complement exists normally in the plasma. 

Metchnikoff and Ehrlich hold divergent views 
concerning the action of antitoxins, the former be- 
lieving that antitoxins stimulate the phagocytes to 
an increased absorption and consequent destruc- 



Compatibility 



214 INFECTION AND IMMUNITY. 

tion of the toxin, whereas Ehrlich claims that 
antitoxin neutralizes toxin by combining chemi- 
cally with it. 

According to Metchnikoff, all types of immunity 
depend, directly or indirectly, on phagocytic activ- 
ity. While the side-chain theory is not in har- 
mony with such a broad assumption, it carries 
with it no denial of the phenomenon of phagocyto- 
sis nor of its importance in certain infections. 

From these selected considerations it is seen 
that the two theories do not stand to each other in 
of theories, the relation of antitheses, and in the light of pres- 
ent knowledge it would seem unwarranted to cling 
to one view to the absolute exclusion of the other. 
It does not follow that because demonstrable 
serum properties explain immunity to one disease, 
or to a certain group of diseases, that recovery 
from all diseases must depend on properties of the 
serum; nor because phagocytic activity explains 
recovery in certain instances that recovery from 
all diseases must depend on a similar activity. The 
conditions which exist in each disease, of course, 
must be recognized independently. It so happens 
that recovery from a certain group of diseases, 
e. g., staphylococcus, streptococcus and pneumo- 
coccus infections, is not accompanied by the de- 
velopment of conspicuous antitoxic or bactericidal 
properties in the serum, but they are characterized 
by a great increase in the number of circulating 
leucocytes (microphages), cells of known phago- 
cytic and bactericidal power, whereas the opposite 
conditions are found in certain other diseases, e. 
g., typhoid and diphtheria. If one seeks the most 
apparent explanation in each case, the great leuco- 



OPSONINS. 215 

cytosis would seem to be of prime importance in 
the first group, and the antitoxic and bactericidal 
power of the serum in the second. 

Investigations from various sources render un- opsonins. 
questionable the value of phagocytosis in certain 
infections, and of particular significance is the 
work concerning opsonins which was referred to in 
the preceding chapter. From this work it follows 
that even for the phagocytic destruction of bac- 
teria the serum contains properties which are of 
essential importance. This appears of all the more 
importance from the fact that immunization with 
at least some micro-organisms (streptococcus, 
staphylococcus) causes an increase in opsonins or 
bacteriotropic substances. 

The accompanying illustration, with some modi- 
fications, is taken from "Ehrlichias Seitenketten- 
theorie," by Ludvig Aschoff. The cell used for 
immunization is assumed to be a cell which will 
cause the formation of antitoxin, agglutinin or 
precipitin, and bactericidal amboceptors; the 
diphtheria bacillus is such an organism, consider- 
ing toxin as one of the receptors of the bacillus. 
This means that the bacillus is able to cause the 
overproduction of all three types of receptors. The 
illustration, however, is on the basis of a hypo- 
thetical cell (p. 216). 

A list of immunizing bodies, their anti-bodies, 
and synonyms for complement and amboceptor, 
is also appended (p. 217). 



I1TMUXE SUBSTAXCES. 



217 



List of Immunizing Bodies and Theib Antibodies. 

Antigens or' Products of 
Immunizing immuniza- 
substances. tion. 



List of Im- 
mune Sub- 
stances. 



Toxins. 
Complements 

Ferments. 

Precipitogen- 
o n s sub- 
stances 

Agglutinogen- 
o us sub- 
stances 

Opsinogenous 
substances 
of bacteria 

Cytotoxin pro- 
ducing sub- 
stances 



Precipitins 
Agglutinins 
Cytotoxins 

Hemolysins, 

etc. 



Complement 



Alexin 
Cytase 



Antitoxins. 
Antic o imple- 
ments 
Antiferments 
Precipitins 



Agglutinins 
Opsonins 
Cytotoxins. . 



fHemolysins 
.1 Bacteriolysins 
] Special Cyta- 
le toxins 
Spermotoxin 
Nephrotoxin 
Hepatotoxin 
Neurotoxin 
Syncytioly- 
sin, etc. 



Consisting o f 

two bodies, 

> i. e., comple- 

men t and 

amboceptor. 



Immunization with Antibodies. 



Antiprecipitins 
Antiagglutinins (?) 
Anticytotoxins 

Antihemolysins, 

etc. 



Consisting either of anti- 
complements or antiam- 
boceptors ; the latter 
may be an antibody for 
the complementophilous 
or for the cytophilous 
haptophore of the ambo- 
ceptor. 



Synonyms. 

Amboceptor 

Immunkorper 

Zwischenkorper 

Intermediary body 

Substance sensibilisatrice 

Fixator 

Preparator 

Copula 

Desmon 



CHAPTEE XVI. 



PRINCIPLES OF SERUM THERAPY. 

In the strict sense serum therapy means the in- 
jection of antitoxic or antibacterial serums for 
curative or prophylactic purposes; this is passive 
immunization or direct serum therapy. Active 
immunization, in which the tissues of the individ- 
ual are induced to form antitoxins or antibacterial 
substances as a result of vaccination or protective 
inoculations, may be considered as indirect serum 
therapy. We may, therefore, include tho latter as 
one of the serotherapeutic measures. 

Bearing in mind the significance of the terms 
active and passive immunization, and the fact 
that they may be used for curative and -prophylac- 
tic purposes, the various procedures may be classi- 
fied as follows:* 

I. PROPHYLACTIC INJECTIONS. 

. classifica- A. Active immunization, in which vaccina- 
therapeutic tion and protective inoculations are included, as 
with the organisms of typhoid, cholera and plague. 
Depending on the material injected, the result is 
the formation of antitoxins or antimicrobic sub- 
stances (amboceptors) ; agglutinins are formed in- 
cidentally. 

1. Inoculation of virulent organisms, (a) In- 
oculation with small amounts of a virulent organ- 
ism, i. e., of a non-fatal dose; used principally in 
experimental work, (b) Inoculation with virulent 

* Modified from Deutsch and Feistmantel In "Die 
Impfstoffe und Heilsera," Leipsic. Geo. Thieme, 1903. 



Measures. 



ACTIVE IMMUXIZATIOX. 219 

organisms into a tissue which has some natural re- 
sistance. The success of vaccination against small- 
pox by using virus obtained directly from the dis- 
eased, a method which was practiced in earlier 
times, was probably due to the fact that the virus 
found unfavorable conditions for the development 
of virulence in the skin. In some instances im- 
munization is accomplished more successfully by 
inoculation of bacteria or toxins into the blood 
stream, as in Kittfs method of vaccination against 
symptomatic anthrax and in immunization with 
rattlesnake venom. 

2. Injection of attenuated virus or toxin. At- 
tenuation may be accomplished by air and light 
(chicken-cholera, Pasteur) ; by cultivation at high 
temperatures (anthrax, Pasteur) ; by chemical 
agents (anthrax, Eoux; diphtheria and tetanus 
toxins, Behring and Eoux) ; by desiccation (rabies, 
Pasteur) ; by passing the virus through other 
animals (swine erysipelas, Pasteur). This last 
observation was a most instructive one; passing 
the bacillus through the rabbit several times in- 
creased its virulence for the rabbit but decreased it 
for swine, while passing the organism through the 
dove increased its virulence for swine. 

3. Injection of killed organisms (anthrax, Tous- 
saint; swine plague, Salmon and Smith). This 
is the safest means of vaccinating against cholera, 
typhoid and plague. In the Pasteur treatment of 
hydrophobia the first injection of the dried spinal 
cord probably contains the killed virus. 

4. Injection of bacterial constituents (a) Bacter- 
ial cell plasm (Buchner's plasmin, obtained by sub- 
mitting micro-organisms to high pressure, and 
Koch's tuberculin TE) ; (b) Soluble bacterial 



220 INFECTION AND IMMUNITY. 

products (the bacterial proteins, as Koch's old 
tuberclin and mallein; the soluble toxins; 
products of bacterial autolysis). When toxins 
are injected antitoxins are formed. The 
autolytic products of some organisms, e. g., 
typhoid and dysentery, cause the formation of bac- 
tericidal amboceptors and agglutinins, but not 
antitoxins. 

B. Passive immunization: the prophylactic in- 
jection of antibacterial and antitoxic serums. 

C. Mixed active and passive immunization: the 
simultaneous injection of an immune serum with 
the corresponding organism, which may be killed 
or living. The serum causes immediate, though 
temporary, resistance, and, in the meantime, an 
active, more permanent immunity develops as a 
consequence of the injection of the organisms. 
This method has been practiced with swine plague, 
swine erysipelas, rinderpest, and experimentally 
in typhoid, cholera and plague. 

II. CURATIVE INJECTIONS. 

A. Active immunization. 

1. Injection of killed micro-organisms in small 
doses with the intention of hastening antibody for- 
mation, as suggested by Fraenkel in the treatment 
of typhoid fever ; value not yet demonstrated. 

B. Passive immunization. 

1. "With antitoxic serums: diphtheria, tetanus, 
snake bites, plague, tuberculosis (?), typhoid (?), 
streptococcus infections (?), etc. 

2. With antibacterial serums: typhoid, cholera, 
plague, dysentery, streptococcus (?), staphylococ- 
cus (?) and pneumococcus (?) infections. 

In general, serums to be effective must have a 



AXTITOXIC THERAPY. 221 

certain strength. When diphtheria antitoxin was General 
first used preparations were put on the market of "serums. 
which contained twenty or fewer antitoxin units 
per cubic centimeter, a strength which would, 
necessitate the injection of 150 c.c. or more in or- 
der to introduce 3,000 units. Much of the early- 
criticism of diphtheria antitoxin is traceable to the 
low value of the serums used at that time rather 
than to an injurious effect on the patients. If 
diphtheria antitoxin now contains less than 250 
units per c.c. it is considered unfit for use; many 
serums contain 500 or more units per c.c. 

Antitoxic and other serums should be free from 
micro-organisms and toxins. The cases of tetanus 
which developed in St. Louis following the injec- 
tion of diphtheria antitoxin will be remembered. 
With correct governmental supervision of the 
manufacture of serums, such accidents are entirely 
preventable. 1 

For the sake of simplicity we may consider the 
principles involved in serum therapy under the 
three topics of (a) antitoxins, (&) bactericidal or 
antibacterial serums, and (c) vaccination. 

(a) axtitoxixs. 

It has been sufficiently emphasized that neutral- Antitoxins. 
ization of toxin by antitoxin implies a chemical 
union between the two substances. When the two 
are mixed outside the body at a given temperature 
and at a given concentration, the rapidity and com- 
pleteness with which the union occurs depends 
only on the degree of affinity which one has for the 
other. There is no third substance with which one 
or the other may unite. In the body, however, the 

1. See appendix to Chapter VII (Part I). 



222 INFECTION AND IMMUNITY. 

conditions are more complex ; in this case two com- 
binations are possible for the toxin, one with the 
antitoxin which has been introduced and a second 
with the tissue cells. As an instance of the great 
rapidity with which toxin may unite with cells, 
the work of Heymans with tetanus toxin may be 
cited. "Hejrmans found that, if all the blood were 
removed from an animal a few minutes after the 
injection of a single fatal dose of tetanus toxin 
and the blood of another animal substituted, still 
the animal died of tetanus" (Ritchie) ; that is to 
say, all the toxin had been bound by the cells in 
that brief time. 
Binding: of Other experiments show that quantities of toxin 
T?ss"es V . and antitoxin which are neutral when mixed be- 
fore injection are not entirely neutral if injected 
separately and at different points of the body. In 
this instance some of the toxin has had time to 
unite with tissue cells before it could come in con- 
tact with the antitoxin. 

Certain work by Donitz illustrates not only the 
rapidity with which toxin may be bound by the 
tissue, but also the method by which antitoxin ef- 
fects a cure. In relation to tetanus he found that 
if the toxin were injected first and the antitoxin 
four minutes later, a quantity of antitoxin, which 
was slightly in excess of the neutralizing dose, was 
required to prevent the development of tetanic 
symptoms; if he waited eight minutes, six times 
as much antitoxin; after sixteen minutes, twelve 
times as much; after one hour, twenty-four times 
the simple neutralizing dose was required. A few 
hours later no amount of antitoxin could save the 
animal. Similar conditions were met in the neu- 
tralization of diphtheria toxin by its antitoxin in 



CURATIVE ACTION. 223 

the body. Madsen, in performing what he called 
"Curative Experiments in the Keagent Glass," 
found that the longer tetanolysin had been in con- 
tact with erythrocytes, the more antitetanolysin 
was required to tear away the toxin from the cor- 
puscles. Practical experience with diphtheria also 
indicates that the longer the disease lasts the more 
antitoxin is required for cure. 

The experiments just cited give us a clear con- Nature of 
ception as to what is meant by the curative action Action. 
of an antitoxin — an action which consists not of 
the neutralization of the circulating toxin, but of 
the wresting away from the tissue of the toxin 
which has been bound. Incidentally the circulat- 
ing toxin is neutralized, and for this step, which 
is essentially prophylactic in nature, the simple 
equivalent of antitoxin is required. But for the 
wresting of toxin from tissue cells not a mere 
equivalent of antitoxin, but a great excess, is re- 
quired, as shown by the experiments of Donitz and 
of Madsen. 

When diphtheria or tetanus has advanced so far 
that no amount of antitoxin will effect a cure, the 
relation of the toxin to the cells has become some- 
thing more than mere chemical union. Further 
processes of a biologic or biochemic nature have set 
in in which the toxin may have become an integral 
part of the protoplasm, and the toxophorous group 
may have begun its destructive action, whatever 
the nature of this action may be. 

It is important to recognize that antitoxin can 
not repair an injury already done by the toxin. 
The repair of the injury depends on the recupera- 
tive power of the cells; hence, antitoxin cures by 
tearing from the cells, perhaps not all, but so much 



224 INFECTION AND IMMUNITY. 

of the toxin that less than a fatal dose remains in 
the cell. 
Two important We may learn from the experiments of Donitz 
rmcipies. ar ^ ^ ]y[ a( } sen ^ wo important principles of anti- 
toxic therapy : First, that of early administration, 
i. e., before a fatal amount of toxin has been 
bound, and, second, the necessity of injecting suffi- 
cient quantities of antitoxin. 

The comparative study of diphtheria and tet- 
anus has clarified the principles of antitoxic 
therapy to no small degree. Knowing that diph- 
theria antitoxin has a much greater curative value 
than tetanus antitoxin, we find some conditions 
which would seem to explain the difference, at 
least in part. 
Tetanus. In regard to tetanus we have the following 
facts: In the test-glass the affinity between the 
toxin and antitoxin is rather weak, since approxi- 
mately forty minutes are required for complete 
neutralization (Ehrlich). On the other hand, the 
experiments of Donitz and of Heymans show that 
the affinity of the toxin for nervous tissue is ex- 
ceedingly strong, all the toxin being taken up 
within a few minutes. These two conditions alone 
suggest the probability of a low curative value on 
the part of the serum. The toxin of tetanus also 
has a remarkable selective action on the most vital 
of all organs, the central nervous system; hence, a 
lower grade of injury may prove fatal than in 
other infections in which less important organs or 
those of greater recuperative power are involved 
chiefly. Furthermore, it seems (Meyer and Han- 
som, Marie and Morax) that the tetanus toxin is 
taken up by the nerve endings and reaches the 
ganglionic cells by way of the axis cylinders, 



PRINCIPLES. 225 

whereas the antitoxin which is injected remains 
chiefly in the blood and lymphatic circulations. 
Hence, the toxin, to a certain extent, is isolated 
and less accessible to the action of the antitoxin. 

Concerning diphtheria, the affinity between Diphtheria-. 
toxin and antitoxin is relatively strong, for com- 
plete neutralization in the test-glass takes place in 
about fifteen minutes (Ehrlich). On the other 
hand, clinical experience indicates that the affinity 
of diphtheria toxin for tissue cells is less than that 
of tetanus toxin, for diphtheria may readily be 
cured on the second or third day of the disease, 
whereas a cure of tetanus is rarely affected. These 
would seem to be favorable conditions for success- 
ful serum therapy. Although the toxin of diph- 
theria may attack the nervous system, the paraly- 
sis seen in such cases is seldom fatal. On the basis 
of anatomic findings in fatal cases it seems prob- 
able that the greater portion of the toxin is taken 
up by parenchymatous and lymphatic organs, and 
by connective tissues (animal experiments), which 
compared with the nervous tissue are of less imme- 
diate importance for life and have greater recuper- 
ative powers. We may infer from clinical experi- 
ence that diphtheria toxin is so situated in the 
body that it is accessible to the action of the anti- 
toxin. 

We have, therefore, the following factors important 
which apparently are of importance for the sue- {^success. 
cess of antitoxic therapy: 1. The concentration 
(strength) of the antitoxin which is injected. 2. 
Its freedom from contamination and adventitious 
toxins. 3. The time of its administration. 4. The 
quantity injected. 5. The degree of affinity be- 
tween toxin and antitoxin. 6. The degree of affinity 



226 INFECTION AND IMMUNITY. 

between toxin and tissue cells. 7. The amount of 
toxin which may be bound without a fatal issue, of 
which the vital importance of the organs involved 
and their recuperative powers are factors. 8. The 
location of the toxin in the body, i. e., its accessi- 
bility for the antitoxin. 
Prophylactic What has been said relates to the curative ac- 
Antitoxin. tion of antitoxin. It is evident that the action of 
antitoxin, when used as a prophylactic, is of a 
simpler nature, for in this instance the conditions 
approximate those of the test-tube experiment. 
There has been opportunity for the antitoxin to 
become uniformly distributed in the blood and 
lymphatic circulations; hence, it is able to meet 
• and to bind the toxin before the latter comes in 
contact with the receptors of important cells. The 
high value of tetanus antitoxin as a prophylactic, 
a value which has become evident in recent years, 
. probably depends on this condition. 

The immunity which is afforded by a prophy- 
lactic injection of antitoxin is of short duration, 
from two to three weeks; the antitoxin is excreted 
in the urine to a considerable extent, but in part 
may be bound and assimilated by the tissues. 

(b) bactericidal or antibactericidal serums. 

Bactericidal Attention has been directed repeatedly to a 
large group of organisms the toxic constituents of 
which are integrally associated with the proto- 
plasm of the microbes; the toxic substances are 
endotoxins. Certain members of this group, of 
which the typhoid, paratyphoid, colon and dysen- 
tery bacilli and the vibrio of cholera are represent- 
atives, cause the development of strong bacterici- 
dal serums in the immunized animal. In Chapter 



Serums. 



ANTIBACTERIAL SERUMS. 227 

XII, A, it was shown that such serums have no 
power of neutralizing the endotoxins of the corre- 
sponding organisms; hence, whatever prophy lactic 
and curative properties they may have would seem 
to depend on the bactericidal action of the ambo- 
ceptor-complement complex. x\s to whether the 
substances which stimulate phagocytosis, i. e., the 
opsonic or bacteriotropic substances are of impor- 
tance for the intra vitam action of bactericidal 
serums, remains to be definitely established. 

It is common knowledge that bactericidal Curative and 
serums have not been successful curative agents, Power** 
although in test-glass experiments they may be 
able to kill large numbers of organisms. Experi- 
mental work has brought to light a number of con- 
ditions which render their ineffectiveness some- 
what intelligible, but this knowledge has been of 
little service in increasing their value, and at this 
moment their outlook as curative agents is not very 
encouraging. 

Animal experiments indicate that, prophylacti- 
cally, they are much more powerful than when 
used as curative agents. Unfortunately, however, 
as in the case of antitoxins, the immunity which is 
conferred is of short duration, the serum being ex- 
creted or the Antibodies destroyed within two or 
three weeks. For this reason they are not suited 
for general prophylactic use in man, but they may 
be distinctly useful when combined with vaccina- 
tion, as indicated later. 

Bactericidal serums are efficient in saving ex- Time ef 
periment animals, provided the serum is injected laiectKn * 
in advance of, simultaneously with or very shortly 
after the bacteria are introduced. By injecting 
the vibrio of cholera and anticholera serum simul- 



228 INFECTION AND IMMUNITY. 

taneously one may readily save a guinea-pig from 
ten times the fatal dose, or more. If the culture 
be injected first and the serum later a larger 
amount of serum is required to save the animal. 
After a few hours a sufficient amount of serum to 
kill all the vibrios may be injected, yet the ani- 
mal will die from the action of the endotoxins 
which have been liberated. The organisms had 
proliferated to such an extent that the mass, 
though dead, contained a fatal amount of endo- 
toxin. A statement made previously may be re- 
peated, that the administration of a bactericidal 
serum rather than being beneficial may actually be 
injurious, in that it dissolves the micro-organisms 
rapidly, an excessive amount of endotoxin thereby 
liberating; this, perhaps, is not definitely estab- 
lished as a point of practical importance. 

Having determined the amount of a bactericidal 
serum which is able to save a guinea-pig from an 
incipient infection, one may calculate on the basis 
of weight the amount which would be required to 
save a man under the same conditions ; frequently 
it amounts to impossible quantities, hundreds of 
cubic centimeters. The conditions are all the less 
promising when we remember that physicians are 
usually called on to treat well-established rather 
than incipient infections. 
Peculiarities of Other conditions which operate against the ef- 
fectiveness of bactericidal serums as curative 
agents have to do with peculiarities of comple- 
ments and amboceptors. The lability of comple- 
ment involves certain difficulties. A bactericidal 
serum, as one would purchase it, contains none, 
because of its spontaneous degeneration. Theo- 
retically, this difficulty may be obviated in three 



Complement 
and Ambo- 
ceptors. 



SUITABLE COMPLEMENT. 229 

ways : First, one may use serums which are fresh 
from the immunized animal ; second, one may com- 
plement the solution of amboceptors (old immune 
serum) by the addition of fresh serum from a nor- 
mal animal which is known to contain suitable 
complement ; or, third, one may inject the comple- 
ment-free serum and place reliance on the comple- 
ment which exists in the plasma and lymph of the 
patient for activation of the amboceptors. It is 
sufficiently established that none of these proce- 
dures enhances the curative value of the serums to 
a satisfactory extent. 

Regardless of the amount of foreign comple- Absorption 
ment which is introduced, it appears to be di- Sy the Tissue"! 
verted from its function. It has been shown ex- 
perimentally that the tissues may absorb a foreign 
complement, and the mere fact that anticomple- 
ments are formed so readily indicates that comple- 
ment may be bound by the tissues. In accordance 
with a rather general principle, if the animal 
which furnishes the serum is remote from man 
zoologically there is all the more likelihood of the 
complement being fixed by human tissues. 

It has been suggested that if one should choose choice of 
for immunization animals which are closely re- immunization. 
lated to man, as chimpanzees and monkeys, a 
double advantage would be gained : First, the for- 
eign complement may be identical or similar to 
that in man and consequently would be less likely 
to be absorbed by the tissues; and, second, the 
complementophilous haptophores of the ambocep- 
tors may be so constructed that human comple- 
ment would serve for activation. Theoretically, 
the conditions would be ideal if immune human 
serum were available for therapeutic purposes. 



Complement. 



230 INFECTION, AND IMMUNITY. 

If one depends on the complement in the p'a- 
tienfs body for activation of the amboceptors, 
there are two possible difficulties of importance: 
First, the native complement of the body is often 
decreased during infections and in some chronic 
diseases and may be too little for thorough activa- 
tion; second, the amboceptors of the immune 
serum may demand for their activation a comple- 
ment or complements which the body does not con- 
tain. 
Diversion of Diversion of complement has been referred to as 
a phenomenon seen in test-tube experiments. In 
this condition an excess of amboceptors in some 
way decreases the power of the serum; by an ex- 
cess of amboceptors one means, in this instance, 
such a quantity that many are unbound by the 
bacteria. It is supposed that a certain amount of 
the complement is absorbed by free or unbound 
amboceptors, hence the effect is like that of too 
little complement. In the desire to administer a 
sufficient amount of antibodies, so much may be 
introduced that diversion of the complement oc- 
curs in the body. Eesults obtained by Loffler and 
Able, by Pfeiffer and by Buxton and others, in 
which excessive doses of immune serum were less 
protective than moderate doses, show that a simi- 
lar phenomenon occurs in the body. 
inaccessibility In certain diseases the microbes are so situated 
that a serum as ordinarily administered may not 
be able to reach them. Pfeiffer thinks that there 
is little hope for the serum treatment of cholera 
because of the exclusive location of the living or- 
ganisms in the intestinal tract. In typhoid also 
the intestines are a reservoir of typhoid bacilli, 
although the living organisms reach the circula- 
tion in abundance. 



of Microbes. 



SUMMARY. 231 

By way of summary, the following conditions 
appear as factors in the low curative value of bac- 
tericidal serums: 1. Bactericidal serums are not 
antitoxic. 2. They may liberate an excessive 
amount of endotoxin by dissolving the bacteria. 3. 
The lability of exogenous complement. 4. The 
power of the tissues to absorb the complements of 
a foreign serum. 5. The lack of a sufficient 
amount of suitable complement in the human 
body. 6. The difficulty of obtaining amboceptors 
for which human complements are suited. 7. The 
possibility of diversion of complement by an ex- 
cess of amboceptors. 8. Inaccessibility of the 
micro-organisms in certain infections (cholera, 
typhoid) . 

As pointed out elsewhere, another group of or- other "Anti- 
ganisms, the members of which contain endo- 
toxins, causes the formation neither of antitoxins 
nor of bactericidal serums; streptococcus, staphy- 
lococcus, pneumococcus, etc. Many investigators, 
nevertheless, are positive in their claims that the 
antiserums for these organisms have a protective 
and even a curative value. The properties on which 
their value depends have not been satisfactorily 
ascertained. Although certain antistreptococcus 
serums are said to be antitoxic, it is contended by 
others that they act by simulating phagocytosis. 
Work now in progress promises to show that im- 
munization with these organisms causes an in- 
crease in the opsonins. Their curative value is 
very low in experimental work and they fail totally 
if injected a few hours subsequent to the introduc- 
tion of the organisms. Clinically, we are familiar 
with them as failures. . 

It is particularly in relation to the streptococ- 



bacterial' 
Serums. 



232 INFECTION AND IMMUNITY. 

cus that the s6-called polyvalent serums have been 
prepared. Cultures of streptococcus obtained 
from numerous sources are used in the immuniza- 
tion with the expectation that the serum will be 
effective against various strains of streptococci. 
The principle may be an important one in the 
preparation of other antibacterial and bactericidal 
serums. 

(C) VACCINATION. 

Vaccination or We are most familiar with the terms vaccine 
Pr0 ocuVat e ion! an( l vaccination as applied to protective inocula- 
tion against smallpox. They are used, however, 
with equal propriety in all instances in which the 
attenuated or killed virus of a disease is inoculated 
for the purpose of establishing resistance to an 
infection. The process set in motion by vaccina- 
tion is one of active immunization in which the 
cells are induced to form specific antibodies over a 
long period; hence, the* resistance is more pro- 
tracted than that established by passive immuni- 
zation. 

Certain experimental work, as previously stated, 
indicates that the acquired resistance persists after 
the formation of antibodies has ceased, even after 
the quantity of the latter has sunk to the normal. 
This condition has been explained by assuming 
that, as a consequence of vaccination, the cells of 
the body have been "trained" to produce the cor- 
responding receptors; hence, when the micro-or- 
ganisms gain entrance at a subsequent time new 
antibodies are formed so rapidly and in such abun- 
dance that the incipient infection is overcome. 

In some instances the nature of the virus used 
is unknown, as in smallpox and hydrophobia; in 
all probability, however, it consists of micro-or- 



VACCINATION. 233 

ganisms rather than of toxins alone. In the case 
of typhoid, cholera, plague and other diseases of 
known etiology pure cultures, living or killed, are 
inoculated. Protection does not follow immedi- 
ately on the inoculation. We are sufficiently fa- 
miliar with this fact in relation to smallpox, in 
which several days are required for the formation 
of a protective amount of the antibodies. There 
is reason to believe that the interval between the 
inoculation and the appearance of antibodies is 
characterized by a decreased resistance on the part 
of the individual, so that during this brief period 
he is unusually susceptible to infection. 

That period immediately following the injec- Negative and 
tion of a toxin or microbe, in which the quantity Phases? 
of antibodies undergoes a temporary decrease, 
Wright speaks of as the negative phase of the im- 
munization; whereas that period marked by the 
new formation of antibodies is called the positive 
phase. The negative phase lasts from a day or 
two to several days, depending on the quantity and 
nature of the virus injected (typhoid). A second 
injection should not be given during the negative 
phase, since it causes a further decrease in the 
antibodies and prolongs the phase. Wright speaks 
of this as a cumulative negative phase. A cumu- 
lative positive phase, marked by the formation of 
larger amounts of antibodies, may be induced by 
the proper spacing of a number of injections. 

In certain instances the nature of the anti- Nature of 
bodies is known. In typhoid, cholera, plague and 
dysentery, for example, they consist of bactericidal 
amboceptors; agglutinins and precipitins are 
formed incidentally. The amboceptors naturally 
depend on the complement of the body for their 



Antibodies. 



234 INFECTION AND IMMUNITY. 

activation. If the disease is one of unknown etiol- 
ogy the nature of the antibodies is not easily de- 
termined. We should keep in mind the possibil- 
ity that vaccination may cause an increase of the 
opsonins and that the potential phagocytosis may 
thereby become greater. 

In case the incubation period of the vaccination 
is shorter than that of the disease (smallpox, hy- 
drophobia) vaccination usually is successful even if 
practiced within a limited time after exposure to 
infection. 

Vaccination in individual diseases is considered 
in Part II (see also Chapter VI, pp. 57, 58). 

Theoretically it would be possible to immunize 
man against diphtheria and tetanus by inoculating 
with small amounts of the corresponding toxins. 
Such a procedure, for obvious reasons, would be 
unnecessary and unjustifiable. 
Mixed Active It is not unlikely that mixed active and passive 
immunization* immunization will be of great service in some in- 
fections. A successful campaign against rinder- 
pest has been carried on in the Philippines by this 
method. The blood of infected cattle contains the 
virus, which as yet has not been cultivated artifi- 
cially. The serum of cattle which have recovered 
from the disease, or which have been immunized 
cautiously with infected blood, contains the speci- 
fic antibodies. Both the immune serum and viru- 
lent blood are used for the inoculations. The same 
principle has been found effective in experimental 
work with cholera, typhoid and plague. Immedi- 
ate immunity is established by the serum, which 
would eliminate the danger period mentioned 
above, and before the serum disappears entirely 
active immunity develops. 



PART TWO-SPECIAL 



Although a consistent classification of the infec- 
tious diseases, on the basis of immunity, is impos- 
sible at the present time, a certain grouping is de- 
sirable for the sake of convenience. The following 
arrangement of those diseases we are able to con- 
sider is made on a basis which is partly etiologic, 
partly with reference to the pathogenic properties 
of the micro-organisms, and partly to the nature 
of the reactions excited in the body by infection or 
immunization. In some instances nothing more 
than general -analogies suggest themselves as a 
basis for the grouping, which is necessarily provi- 
sional and imperfect. 

GROUP 1. 

Diseases, natural or experimental, which are 
caused by soluble toxins of bacterial, animal or 
plant origin. Infection or immunization induces 
immunity to subsequent attacks (except in hay fe- 
ver), the immunity being characterized by the 
formation of serum antitoxins, and occasionally of 
bacteriolysins and agglutinins. The serums of 
highly immunized animals are protective and cur- 
ative for the corresponding intoxications in mar> 
and other animals. 

A. BACTERIAL DISEASES. 
I. DIPHTHERIA. 

Bacillus diphtheria, or the KJebs-Loefner bacil- 
lus, was discovered by Klebs in 1883, and more 
fully described by Loeffler in 1884. It answers all 



236 INFECTION AND IMMUNITY. 

characterjs- Koch's laws in its relationship to the disease of 
Organism, diphtheria. It is a nonrmotile, rod-shaped organ- 
ism having about the length of the tubercle bacil- 
lus, but twice its thickness. One end commonly 
presents a flask-like enlargement. It stains by 
Gram's method, with the ordinary anilin dyes, and 
with the special stain of Neisser shows a peculiar 
granulation, the granules of Babes-Ernst. It is 
readily cultivated, especially on solid media which 
contain serum and in various bouillons. It tends 
to grow in coherent masses and under the micro- 
scope the cells often show a characteristic phalanx- 
like arrangement. 

The diphtheria bacillus is an obligate parasite 
having no vegetative existence outside of the body, 
is very resistant to desiccation and may remain 
virulent in a dried state for from one to five 
months. Its life in water varies from a few days 
to several weeks, having its shortest existence in 
distilled water and its longest in hydrant water 
which has been boiled. It disappears more quickly 
from unboiled hydrant water. It is very suscepti- 
ble to ordinary antiseptics, being killed in a few 
minutes by corrosive sublimate even in a dilution 
of 1 to 10,000. 

The sources of infection may be enumerated as 
follows : 1. From the false membranes, sputum 
or excretions of the mouth, pharynx,- nose, con- 
junctiva and deeper respiratory passages of in- 
fected individuals. 2. From convalescents and 
those who have fully recovered, even after serum 
treatment. Virulent organisms may persist in the 
pharynx or nose of convalescents for weeks and 
months, as in one of Prip's cases in which they 
were found twenty-two months after recovery. 3. 



Methods of 
Infection. 



DIPHTHERIA. 237 

From the upper air passages of healthy persons 
who may never have had diphtheria, but who have 
been in direct or indirect contact with the dis- 
eased. Kober obtained virulent bacilli from 8 per 
cent, of the individuals who had been in direct 
contact with patients, and he states that 0.83 per 
cent, of the people at large carry with them viru- 
lent organisms. This condition may well account 
for the "spontaneous" origin of diphtheria in the 
susceptible. 4. From cases of latent diphtheria as 
represented by chronic pharyngeal diphtheria and 
chronic rhinitis fibrinosa. 

Hence, infection takes place chiefly by direct 
contact, but frequently also by indirect contact. 
Transmission by kissing or by other means of inti- 
mate contact, by using infected cups or toys, is 
well recognized. "Drop infection," i. e., from in- 
fected globules of mucus or saliva which the pa- 
tient emits when speaking or coughing, may occur, 
but perhaps is not of great significance. The same 
probably is true of "dust infection," although, as 
stated, the organism may remain living and viru- 
lent in a dried state for a long time. The disease 
is rarely transmitted from animals to man, al- 
though such transmission may occur from the cat, 
which occasionally suffers from true diphtheria. 
The diphtheria of fowls is due to another organ- 
ism. 

The upper air passages, more rarely the conjunc- 
tiva, wounds and the vulva, are recognized as in- 
fection atria. 

The local and general phenomena of diphtheria pathogenesis. 
are caused by the soluble toxin which the organ- 
ism secretes. Although the toxin is not absorbed 
through, nor does it injure the unbroken skin, it 



238 INFECTION AND IMMUNITY. 

produces necrosis of the mucous surfaces and un- 
derlying tissue at the site of infection. Through 
• the wounded surface fibrin-forming elements es- 
cape, as a consequence of which successive layers 
of fibrin are deposited and the fibrin, together with 
the necrotic surface, leucocytes and associated 
micro-organisms constitute the membrane which 
so often marks the disease clinically. The local 
process is similar in diphtheria of cutaneous 
wounds. The toxin becomes generalized by absorp- 
tion through the lymphatic circulation. 
Localization of Characteristically the bacilli are confined to the 
the Bacilli. g ^ e ^ i n f ec ft on# Although diphtheritic bacterie- 
mia rarely occurs, the bacilli have been found oc- 
casionally in the blood and viscera of fatal cases. 

The clinical and anatomic conditions lead us to 
believe that the parenchymatous organs, the lym- 
phatic tissues and the cells of the nervous system 
. contain receptors with which the toxin unites, in- 
asmuch as these tissues suffer demonstrable injury 
during the disease. When the toxin is injected 
subcutaneously into animals, localized edema and 
necrosis occur; hence, the connective tissues may 
also take up a portion of the toxin, diverting it, so 
to say, from the more vital organs. 

Mixed Mixed infections render diphtheria a more dan- 
tnfections. g ercms di sease . According to Baumgarten, the 
streptococcus is associated with the diphtheria ba- 
cillus in most cases of diphtheria. The observa- 
tion of Eoux and Yersin that the streptococcus in- 
creases the virulence of the diphtheria bacillus 
both in the test-tube and in animal experiments 
may explain to some degree the severity of the dis- 
ease when accompanied by streptococcus infection. 
Aside from the local influence of the streptococcus, 



Susceptibility. 



DIPHTHERIA. 239 

however, a general invasion by this organism may 
occur, with such consequences as acute nephritis 
or lobular pneumonia, and in this condition the 
diphtheritic infection may fall into the back- 
ground in importance (septic diphtheria). Post- 
diphtheritic suppurations commonly are caused by 
the pyogenic cocci, but sometimes in association 
with the diphtheria bacillus itself. Earely the 
bacillus is found in pure culture in lobular pneu- 
monia, a condition which Flexner and Anderson 
produced experimentally in animals. In puer- 
peral infections with the streptococcus a puerperal 
diphtheria is sometimes superimposed. 

Very young children resist diphtheritic infec- immunity and 
tion. A certain degree of immunity may be trans- 
mitted by the mother. Observations on animals 
show that when the blood and milk of the mother 
contain antitoxin, the offspring acquires some pro- 
tection, which, however, may disappear after the 
cessation of nursing. Polano claims that anti- 
toxin passes from the mother to the child through 
the placenta. From the second to the seventh or 
eighth year children usually are very susceptible. 
This susceptibility is not uniform, however, for 
many children escape infection, whereas others, 
under the same conditions, contract the disease. 
Following this period susceptibility decreases and 
after the fifteenth year the disease is relatively 
rare. 

The cause of the immunity which develops in 
the absence of a preceding infection has not been 
sufficiently investigated. In some cases consid- 
erable amounts of antitoxin are found in the 
serum, perhaps enough to account for the immun- 
ity. The prolonged presence of bacilli of low 



Immunity. 



240 INFECTION AND IMMUNITY. 

virulence in the nose or pharynx, or mild attacks 
of the disease which have not been recognized, 
may cause the development of antitoxin. As stat- 
ed in an earlier chapter, the loss of suitable re- 
ceptors may be a factor in this type of acquired 
immunity. 

Hypertrophic tonsils and chronic pharyngitis 
appear to be predisposing causes in children. 
Active Spontaneous recovery (active immunity) is due 
solely to the formation of the specific antitoxin 
by the tissues of the patient. We may regard the 
relationship of the leucocytes to diphtheritic in- 
fection as not definitely settled. Although leuco- 
cytosis is a fairly constant occurrence and may go 
as high as 25,000 to 30,000 to the cubic milli- 
meter, it is difficult to dissociate that due to the 
diphtheritic infection from that caused by a mixed 
infection with the streptococcus. Both polynu- 
clears and mononuclears are increased, the latter 
being especially marked in children (Ewing). 
That the polymorphonuclear leucocytes may ingest 
diphtheria bacilli was shown by Wright and Doug- 
lass, the influence of opsonins being essential for 
phagocytosis. Certain observers hold that a 
marked leucocytosis is an unfavorable prognostic 
sign, although Besredka and others take the oppo- 
site view. 

The duration of active immunity to diphtheria 
varies greatly. Usually an individual has diph- 
theria but once, yet not infrequently those are en- 
countered who suffer from repeated attacks. In 
some instances the susceptibility continues into, 
adult life. 
Prophylaxis. The advent of serum therapy justifies no relaxa- 
tion in the customary prophylactic measures, such 



DIPHTHERIA. 241 

as isolation of the diseased, quarantine and disin- 
fection. A patient should not be considered harm- 
less until his month, phar}mx and nose are free 
from bacilli, a condition which may be brought 
about by antiseptic applications, and for the de- 
termination of which repeated bacteriologic exam- 
inations are necessary. The danger that others 
who have been in contact with the patient may 
carry the infection should be met by appropriate 
treatment. It is not to be forgotten that anti- 
toxin does not destroy the organisms. The injec- 
tion of antitoxin is our most effective measure for 
individual prophylaxis. 

The efficacy of diphtheria antitoxin is so well serum 
known that little comment is needed. It has Therapy * 
caused a reduction of more than 50 per cent, in 
the mortality of the disease; from 41 per cent, to 
8 or 9 per cent., according to Baginsky. 

For prophylaxis from 500 to 1,000 units are 
generally recommended, although some foreign 
authorities give only 250 units. Earely, individ- 
uals who have received such treatment develop 
diphtheria within twenty-four hours after the in- 
jection. In these cases it is probable that infec- 
tion has already occurred and symptoms appear 
before the antitoxin is thoroughly distributed. 
Naturally one may contract diphtheria after the 
antitoxin is eliminated. 

For curative purposes the amount actually re- 
quired depends on the virulence of the infection 
and the duration of the disease. Inasmuch as the 
virulence may not be known accurately, what ap- 
pears to be an excess of antitoxin is always de- 
manded. Having in mind the average dose of 
3,000 units recommended by the recent edition of 



242 INFECTION AND IMMUNITY. 

the United States Pharmacopeia, the physician 
must be guided by the conditions in the individ- 
ual case. Less than 2,000 units are rarely indi- 
cated, and as many as 10,000 and 14,000 units 
may be given without detriment to the patient. 
There should be no hesitation about repeating a 
dose within twenty-four hours in the absence of 
distinct improvement. 

Eansom and Knorr state that if the antitoxin 
"is given intravenously, which may be done without 
danger, the action of the serum is about eight 
hours earlier than when given subcutaneously. In 
severe and in late cases it is advisable to use this 
method of introduction, the serum first being 
warmed to the temperature of the body. 

It is probable that few cases are so mild ot so 
hopeless, unless moribund, that the omission of 
antitoxin is justifiable. 
Diphtheritic The belief that antitoxin favors the development 
Paralysis. Q ^ diphtheritic paralysis is no longer held. If 
there has been an actual increase in the percentage 
of cases which suffer from paralysis, as sometimes 
stated, it is because a larger number of severe 
cases is saved ; and the severe cases are those which 
most frequently develop paralysis. If we accept 
the view of Ehrlich that a special toxin of weak 
affinity for the antitoxin, i. e., the toxon, causes 
the paralysis, we find all the more justification 
for large doses of antitoxin, for antitoxin neutral- 
izes the toxon as well as the toxin. On the basis 
of experimental work Ransom concludes: "Trans- 
ferring the results (of experiments) to practice 
among human beings, we may expect liberal doses 
of antitoxin given early in the illness to influence 
favorably the subsequent paralysis; and this fa- 



DIPHTHERIA. 243 

vorable influence is likely to manifest itself, not so 
much in the local paralyses (soft palate, etc.), as 
in such fatal symptoms as failure of the heart. 
Severe cases, however, are likely to be followed by 
some paralysis in spite of even large doses of anti- 
toxin." 

Cases in which there is severe mixed infection, 
septic diphtheria, respond less favorably to anti- 
toxic therapy than uncomplicated cases. At some 
time a mixed serum therapy suited to the mixed 
infection may be possible. 

The suggestion made by Wasserman of a com- 
bined treatment with bactericidal and antitoxic 
serums has not been applied practically. 

Inasmuch as the serum of the patient does not Agglutination 
develop agglutinins, the agglutination test is of Tes1, 
no value for the recognition of the disease. If ani- 
mals are immunized with the bacillus, agglutinins 
are said to be formed. The serum of such an ani- 
mal may be used for the identification of a culture 
made from the throat, but this would have no 
practical value, for the diagnosis may be estab- 
lished by the ordinary bacteriologic methods much 
more quickly and satisfactorily. It is difficult to 
obtain a homogeneous suspension of the bacillus 
for the agglutination test. 

Microscopically and culturally the bacillus of Pseudodiph 
diphtheria can be distinguished with difficulty theria BacillL 
from a variety of other organisms which belong to 
the same group^ and which are called pseudodiph- 
theria bacilli. The latter are frequently found in 
diphtheritic throats, but occur also in the upper 
air passages and conjunctiva in the absence of all 
lesions. On the whole, they are non-pathogenic, 
but occasionally a culture is found which causes a 



244 INFECTION AND IMMUNITY. 

subcutaneous infiltration at the point of injection 
in an experimental animal. Hamilton cultivated 
one which was distinctly virulent for animals. Their 
pathogenicity, however, is a ] together different 
from that of the diphtheria bacillus inasmuch as 
diphtheria antitoxin does not protect against them 
nor do animals which are immunized with pseudo- 
diphtheria bacilli become immune to the toxin of 
diphtheria. The Bacillus xerosis, which is thought 
by some to be the cause of xerosis conjunctivae, 
but which is also found under normal conditions, 
is a pseudodiphtheria bacillus. The animal experi- 
ment is the only positive means of differentiating 
the true from the pseudodiphtheria bacilli. Some 
consider them as diphtheria bacilli which have lost 
their virulence. 

The presence of these organisms may complicate 
the diagnosis of diphtheria in some cases, but 
there is little danger of serious error. If one 
found organisms resembling the bacillus of diph- 
theria in a membranous sore throat which was ac- 
companied by severe symptoms, there could be no 
wavering in the decision to use antitoxin. 

II. TETANUS. 

In 1884 Carle and Eattone demonstrated the 
infectiousness of tetanus by inoculating the pus 
from an infected wound into rabbits; 11 of the 12 
inoculated rabbits died of tetanus. In 1885 the 
bacillus was discovered by Mcolaier, and Kitasato 
cultivated it artificially in 1889. 
Characteristics The organism is rather long and slender (2 to 
° f organism! 4 microns long, 0.3 to 0.5 broad), possesses many 
flagella and has a small amount of motility. It 
stains readily with the ordinary anilin dyes and by 



TETANUS. 245 

Gram's method. In young cultures isolated cells 
and threads predominate, but after a few days 
spore formation begins; eventually all the adult 
cells degenerate and the culture consists entirely 
of spores. The spores have a larger diameter than 
the bacillus, are situated at one end of the cell and 
give the latter the characteristic "drumstick" 
form. The organism is a strict anaerobe and is 
obtained in pure culture with some difficulty. 
Morphologically it is difficult to distinguish from 
the bacilli of malignant edema and symptomatic 
anthrax. 

Few organisms are distributed more widely and Habitat. 
generously than the bacillus of tetanus. It is most 
abundant in street dirt and in tilled ground which 
has been fertilized with manure. Xicolaier found 
it in twelve out of eighteen samples of earth. It 
is less abundant in timber land. Such a distribu- 
tion is easily accounted for, since the bacillus 
seems normally to be an inhabitant of the intesti- 
nal tract of the horse, cow and sheep, and is often 
found in that of man and other animals. It oc- 
curs on dirty clothing and readily gains access to 
dwellings with dust in which it may be blown and 
carried about. Tetanus frequently develops in 
gunshot wounds in which dirty clothing is carried 
into the tissue, and several instances of house 
tetanus have been noted in which a number of in- 
dividuals in the same dwelling have contracted the 
disease following injury. Particular localities may 
be heavily infected. In certain tropical districts a 
large percentage of the new born die of tetanus 
neonatorum, and puerperal tetanus has prevailed 
alarmingly in Bombay. It has been suggested 
that the custom of bleaching the linen on the 



246 INFECTION AND IMMUNITY. 

ground may be responsible for the prevalence of 
the disease in these localities, but from the fact 
that it has decreased under aseptic practices the 
general lack of surgical precautions is probably of 
greater importance. Tetanus has resulted from 
the injection of impure gelatin for hemostatic 
purposes. The bacillus has been found in sea 
water. 

The ability of the bacillus to proliferate outside 
the animal body has not been determined. Some 
observers hold that it exists as a vegetative organ- 
ism only in the intestinal tract of animals, but the 
possibility of proliferation in soil is by no means 
excluded, particularly since it is so often found in 
association with organisms which are known to 
favor its growth. When incrusted in solid ma- 
terial and accompanied by suitable saprophytes it 
may readily find the anaerobic conditions which 
are demanded for germination of the spores. 
Resistance. The spores are very resistant. In one instance 
they remained virulent for eleven years on a splin- 
ter of wood. They may be killed in six days by 
direct sunlight. In comparison with non-spore- 
forming organisms they are very resistant to anti- 
septics. Kitasato found that they were killed in 
five minutes by steam, in fifteen hours by a 5 per 
cent, carbolic acid, in two hours by 5 per cent, 
carbolic acid to which 0.5 per cent, of hydro- 
chloric acid was added, in three hours by 1/1000 
corrosive sublimate and in thirty minutes by the 
same solution to which 0.5 per cent, hydrochloric 
acid had been added. 

Tetanus is conspicuously a wound infection and 
that it develops so frequently from wounds which 
are contaminated with earth is readily understood 



TETANUS. 



247 



from the distribution of the organisms as cited infection Atria 

, /~i ■ i ■ i ,i i j» and Conditions 

above. Considering, however, the great number ot which Favor 
such wounds and the prevalence of the bacillus, n ect,0,, • 
the rarity of the disease is remarkable. In expla- 
nation of this fact investigations have shown that 
the organism is not a vigorous parasite, that it 
demands special conditions for its development in 
the tissues. According to Yaillard and Eouget, 
the spores when washed free of toxin do not cause 
tetanus, but rather are taken up and destroyed by 
leucocytes. 

The bacillus, furthermore, is a strict anaerobe, Anaerobic 
demanding for its development a wound from fn wounds. 
which the air is largely excluded. It is well known 
that penetrating wounds in which infected ma- 
terial is carried beneath the fasciae, as the rusty 
nail wounds, also those accompanied by deep lac- 
erations, as wounds inflicted with blank cartridges, 
or those in which dirt and micro-organisms have 
been ground into the tissues, as in crushing inju- 
ries, are prone to be followed by tetanus. Under 
such conditions the bacillus lies deeply imbedded 
in the tissues and remote from the air. 

Of equal importance is the presence of foreign 
matter and particularly of other micro-organisms. 
Relatively superficial wounds in which there is 
laceration of the tissue with consequent necrosis, 
as in wounds by toy pistols, even the paper-cap 
pistol, are well adapted for the development of 
tetanus if the germs were on the skin at the time 
of injury. Xecrotic tissue favors the proliferation 
of the tetanus bacilli in two ways. In the first 
place it seals up the wound to a certain extent, 
and thus provides the requisite anaerobic condi- 
tion ; in the second place it would seem to prevent 



Inhibition of 
Phagocytosis. 



-?• 



248. INFECTION AND IMMUNITY. 

phagocytosis of the bacilli in some obscure way. 
It has been suggested that the strong, chemotactic 
relation which exists between necrotic material 
and leucocytes causes the latter to take up the dead 
tissue rather than the bacilli. That innocent for- 
eign material may favor the development of teta- 
nus in the presence of the microbes was shown by 
Vaillard and Eouget: tetanus would develop in 
the presence of an artificially produced hematoma 
or a subcutaneous fracture while in the absence of 
such predisposing factors the bacilli were taken up 
by phagocytes. 
Mixed Saprophvtic organisms and the pus-producing 

Infections. • -. • i_ n £ -, ■ j • 

cocci which are usually found m wounds contami- 
nated with earth appear to favor the development 
of tetanus. This may be explained to some extent 
by their ability to increase the virulence of the 
tetanus bacillus, a condition which is noted in cul- 
tures. In the wound they may engage the leuco- 
cytes in phagocytosis and prevent ingestion of the 
tetanus bacilli. As aerobic organisms they may 
facilitate development of the bacilli by consuming 
local oxygen. 

Our great harvest of tetanus following Fourth 
of July injuries is closely associated in the first 
place with the warm, dry season in which the 
bacilli are more readily disseminated with dust, 
and in the second place with the nature of the 
wound and mixed infections, as described above. 

Occasionally tetanus follows the simplest 
wounds, which may have healed entirely before 
symptoms develop. In "idiopathic tetanus" and 
in the so-called "tetanus rheumaticus," which fol- 
lows exposure to cold, the infection atria are un- 
known. In the latter instance a latent infection, 



TETANUS. 249 

which is stirred into activity by the reduction of 
resistance which often follows exposure, may be 
present: avirulent tetanus bacilli (?) were culti- 
vated from the lungs of one such patient. The oc- 
casional occurrence of tetanus following diphthe- 
ria and typhoid suggests that infection may take 
place through wounds of mucous surfaces. Xeither 
the bacillus nor its toxins penetrate the unbroken 
skin or mucous membranes, and the alimentary 
tract is further protected by the ability of the gas- 
tric and pancreatic juices to digest the toxin. 

The incubation period varies from two or three Period of 
days to several weeks. In the statistics of Eose 20 lncubation - 
per cent, of the cases showed symptoms in the first 
week, 45 per cent, in the secondhand about 30 per 
cent, in the third or fourth weeks. The shorter 
the incubation period the more fatal the disease. 
In the statistics cited the mortality with short in- 
cubation was 91 per cent.; when the incubation 
period was moderate it was 81.3 per cent., and 
when prolonged, 52.9 per cent. The nearer the 
infection atrium is to the central nervous system 
the shorter is the incubation period; "head teta- 
nus" develops quickly. 

The pathogenic properties of the tetanus bacil- Pathogenesis. 
lus reside in its soluble toxins, of which two, teta- 
nospasmin and tetanolysin, are known. The char- 
acteristic nervous phenomena of the infection de- 
pend on the action of the former, whereas the lat- 
ter, a hemolytic toxin, is of minor importance. As 
in diphtheria, a systemic distribution of the bacilli 
is not necessary for the development of the dis- 
ease, the toxin being produced by the organisms iD 
the wound, whence it is carried to the nervous 
tissue by way of the lymphatics. Particularly in 



250 INFECTION AND IMMUNITY. 

mixed infections tetanus bacilli may be carried to 
neighboring lymphatic glands and eventually 
reach the circulation; pure cultures have been ob- 
tained from the heart's blood in experimental 
work. The blood, on account of its content in 
oxygen, is thought to be unfavorable for the 
growth of the organism. 

Just before death the toxin has been demon- 
strated in the blood of man by injecting some of 
the serum into mice. Its excretion in the urine is 
questionable. Tetanus produces no characteristic 
anatomic changes, although degenerative lesions 
in the ganglionic cells occur. Death usually occurs 
from asphyxia caused by contractions of the dia- 
phragm, or muscles of the glottis, or from cardiac 
failure. In some instances the blood has been 
found more or less laked because of the action of 
the tetanolysin. 
Tetanospasmin. Tetanus toxin (tetanospasmin) has a very 
strong affinity for the nervous tissue of susceptible 
animals. This may be demonstrated in test-tube 
experiments in which the toxin is mixed with an 
emulsion of the nervous tissue ; the nervous tissue 
neutralizes the toxin more or less completely, as 
. determined by subsequent inoculations of the mix- 
ture (Wasserman's experiment). It is held by 
certain authorities that the toxin attacks only the 
nervous tissue in man; in some of the lower ani- 
mals, however, various organs, especially the liver, 
have an affinity for the toxin. 

The method by which tetanus toxin reaches the 
central nervous system has been the subject of 
much speculation and experimentation. Kecent 
observations by Marie and Morax and by Ransom 
and Meyer show with a great degree of probabil- 



TETANUS. 251 

ity that it is absorbed by the end organs of the 
motor nerves and from there passes to the gang- 
lionic cells through the axis cylinders. This ab- 
sorption takes place very quickly; when the toxin 
is given intravenously it disappears from the blood 
in the course of minutes. It has been found in the 
nerves within an hour and a half after subcutane- 
ous injection. Its further transmission centrally 
occupies more time and, indeed, the investigators 
mentioned explain the rather long incubation 
period of the disease on the basis of the time re- 
quired for this transmission. The brief incuba- 
tion period in "head tetanus/" accordingly, would 
depend on the short distance the toxin is obliged 
to travel to reach the ganglionic cells. 

Although the toxin appears not to be taken up varieties of 
by the sensory nerves, a painful form of the dis- Tetanus - 
ease, tetanus dolorosa (Meyer), may be pro- 
duced experimentally by injecting the toxin into 
the posterior roots of the spinal nerves. Eoux 
caused "cerebral tetanus" by introducing the toxin 
into the cerebral tissue; the condition is charac- 
terized hj absence of contractures. fr Local teta- 
nus," in which the muscles in the vicinity of infec- 
tion or inoculation are involved in contractures, is 
the first symptom of tetanus in experiment ani- 
mals; it rarely occurs in man except in head teta- 
nus. The phenomenon depends on the fact that 
the toxin, being transmitted through the motor 
nerves, reaches first the ganglionic cells which cor- 
respond to the infected area. 

According to Metchnikoff, the only natural im- immunity 
munity which man possesses to tetanus is leuco- 
cytic and this may be sufficient to protect under 
favorable conditions. The observations of Vaillard 



252 INFECTION AND IMMUNITY. 

and Bouget (cited above) support this claim. Sus- 
ceptibility depends not only on the presence of 
suitable receptors in the nervous tissue, but also 
on the degree of affinity which exists between 
these receptors and the toxin. In man and some 
animals this affinity is very great, whereas in fowls 
it is weak and an enormous amount of toxin is re- 
quired to cause tetanus. A further proof of this 
weak affinity in non-susceptible animals rests in 
the fact that the toxin when injected into the blood 
remains unabsorbed for a long time, whereas in 
susceptible animals it disappears very quickly. Ac- 
quired immunity depends on the presence of anti- 
toxin in the circulation. 
Prophylactic Tetanus antitoxin is a thorough prophylactic. 
Antitoxin. This fact has been heralded so extensively in re- 
cent years that there can be little excuse for ignor- 
ance on the part of any physician. At the same 
time, the returns from the "Fourth" show that the 
principle is not yet deeply imbedded in the medical 
mind. It is quite certain that a large percentage 
of these fatalities could be prevented by two injec- 
tions of antitetanic serum, one at the time of in- 
jury and a second from five to eight days later. 
An epidemic of puerperal tetanus in an obstetric 
ward in Prague was checked by prophylactic injec- 
tions of the antitoxin. In a certain section of 
France 4,000 horses, with injuries commonly fol- 
lowed by tetanus, received antitoxin and none de- 
veloped the disease. 

No degree of efficacy on the part of the anti- 
toxin, however, justifies disregard of the surgical 
care which the wound demands. From the facts 
cited it is clear that thorough and frequent disin- 
fection of the wound, free drainage, the removal 



TETAXUS. 253 

of all foreign and necrotic material, and the ac- 
cess of air are measures of eminent importance. 
Punctured wounds should be opened up. Anti- 
toxin, preferably as a powder, may be used in the 
wound, and the serum infiltrated into the adjacent 
tissue. 

The principles which apparently underly the ill curative Value 
success of the antitoxin as a curative agent were ofAnt,toxm - 
treated of in Chapter XVI, Part I. Its adminis- 
tration as early as possible after symptoms have 
appeared is demanded. After symptoms have ex- 
isted for more than thirty hours Behring main- 
tains that there is no hope of cure by the subcuta- 
neous route. Inasmuch as forty hours or more are 
required for complete absorption from the subcuta- 
neous tissue, intravascular injection of at least the 
first dose would seem to be indicated. Yet by 
neither of these methods is the most essential end 
accomplished, for the antitoxin does not reach the 
nerves nor can it be recognized in the cerebrospinal 
fluid in conspicuous quantities. The most that 
such injections accomplish is the neutralization of 
the circulating toxin, that which is not yet on its 
way to the central nervous system through the mo- 
tor nerves. It is, of course, important to neutral- 
ize the circulating toxin and it must be done quick- 
ly, for in the course of a few hours the fatal quan- 
tity of toxin may have been absorbed; "a dose of 
antitoxin which would save in the morning may 
be without effect in the evening." 

At the same time it is of greater immediate im- Method of 
portance to neutralize that which has already en- AnSSwin. 
tered the peripheral nerves, and if possible to tear 
away some of the toxin already bound by the gang- 
lionic cells. To accomplish this object, or to at- 



254 INFECTION AND IMMUNITY. 

tempt it, special procedures are demanded. We 
may then consider the antitoxic treatment as fol- 
lows : 

First: The neutralization of the toxin which 
has already been absorbed by the peripheral nerves 
and spinal cord at a point as near the vital centers 
as possible. This involves surgical exposure of the 
large nerves of the part as near the trunk as possi- 
ble and their infiltration with antitoxin (Eansom 
and Meyer)/ and in desperate cases the infiltra- 
tion of the antitoxin in the spinal cord in the 
vicinity of the medullary centers. From five to 
fifteen minims may be injected into the nerve 
trunks at a sitting, and the operation may be re- 
peated on subsequent days; the needle should be 
partially withdrawn and reinserted in different di- 
rections during the injection. Eogers recommends 
tying loose ligatures around the nerves after the 
operation so that they may be readily drawn up 
and identified for further injections. In order to 
reach the medulla the intracerebral method of 
Eoux or that of Eogers may be utilized. Kocher 
has devised a technic for the intracerebral injec- 
tions. Anterior to the parietofrontal suture and 
to one side of the median line the scalp is pre- 
pared, and a hole drilled through the skin and 
skull, having its direction toward the foramen 
magnum. By means of a long needle, the ventri- 
cle is penetrated and the serum, after injection, 
finds its way to the fourth ventricle to the imper- 
iled respiratory and cardiac centers; 10 c.c. may 
be injected. Eogers seeks to accomplish the same 
end by a different technic. He introduces the 
needle between the sixth and seventh cervical ver- 
tebrae, punctures the cord deeply, and injects from 



TETANUS. 255 

20 to 30 minims at a sitting. Although there is 
danger of intraspinal hemorrhage in the proce- 
dure, no ill effects were noted. It has been recom- 
mended also that the cerebrospinal fluid be with- 
drawn by means of lumbar puncture and substi- 
tuted by antitoxin. Some physicians who have 
used this method report favorable results. 

Second : The neutralization of all toxin which 
is not yet bound by the nervous tissue or absorbed 
by the motor nerves. This demands the infiltra- 
tion of the wound and surrounding tissue with the 
antitoxin, and injection of a sufficient amount of 
the serum into the circulation in order that circu- 
lating toxin may be neutralized. The intraneural, 
intraspinal or intracerebral injections should al- 
ways be supplemented by subcutaneous or intra- 
vascular injections. The first dose should be given 
intravenously, whereas subsequent injections may 
be given subcutaneously. The injections should 
always be repeated. 

Unfortunately, tetanus antitoxin is not stand- standardiza- 
ardized by American manufacturers and dosage JUxiiu Ant '" 
can not be controlled with any accuracy. Although 
standardization can not be accomplished with the 
same degree of accuracy as in the case of diphthe- 
ria antitoxin, its approximate value can be deter- 
mined (within 5 or 6 per cent.), which is suffi- 
cient for practical purposes. The antitetanic 
serums of Behring, Tizzoni and the Pasteur Insti- 
tute are all standardized, but on somewhat differ- 
ent bases. Behring advises the administration of 
20 units of his serum for prophylactic purposes, 
and 100 units as the "simple" curative dose when 
given soon after the development of symptoms. 

Xot less than 10 c.c. of American serum should 



256 INFECTION AND IMMUNITY. 

be given for prophylaxis, and the dose should be 
repeated. No definite limits can be given as to the 
amount which may reasonably be given for cura- 
tive purposes. Ten cubic centimeters given intra- 
venously at once, and an equal amount subcutane- 
ously on subsequent days, would seem to be suffi- 
cient to neutralize the unbound toxin if the serum 
has reasonable strength. Standardized serums cer- 
tainly are to be preferred. 

Agglutination has no practical significance for 
diagnostic purposes. An agglutinating power has 
been noted in the serum on the eighth day. Ag- 
glutinins may be produced by immunizing animals 
(rabbits) either with the bacilli or the toxin. In 
the latter case the formation of the agglutinin is 
due to the presence of agglutinogenic receptors in 
the toxin solution. 

III. BOTULISM. 

Bacillus Botulism is a peculiar form of meat poisoning 
Botuimus. ^ n ^jgh t ne nervous system is involved princi- 
pally. From twenty-four to thirty-six hours after 
the poisonous meat is eaten salivation, ptosis, dila- 
tation of the pupils and paralysis of the ocular 
muscles develop and death from bulbar paralysis 
occurs rapidly in from 25 to 30 per cent, of the 
cases. In the event of recovery, convalescence may 
extend over weeks or months. 
infected The disease occurs especially in some European 
districts in which improperly preserved or raw 
meats are eaten. The term ichthyosismus is ap- 
plied to a similar or identical disease which is 
caused in Russia by salted fish. In 1895 von 
Ermengem investigated a ham which had caused 
50 cases of botulism, and isolated from it an anae- 
robic, spore-forming bacillus, which produces a 



Meats. 



BOTULISM. 257 

soluble toxin capable of causing the entire symp- 
tom-complex of the disease. 1 The organism pos- 
sesses flagellar has limited motility, grows only in 
alkaline media, and in contrast to most pathogenic 
organisms prefers a relatively low temperature 
(18-25° C). It is probably on account of its 
physiologic activity at such temperatures that it 
is able to produce its toxin in meats which have 
been kept in a cool place. It is found in decom- 
posed ham and various sausages (Leberwurst and 
Blutwurst), and probably gains access to the meat 
after the animal has been killed. Yon Ermen- 
gem investigated two hams from the same animal- 
One was under anaerobic conditions being covered 
with brine, while the other was exposed to air; 
only the former was toxic. The organisms may be 
absent from the superficial portion of the meat, 
but abundant in the deep portion. The spores are 
relatively susceptible to heat, being destroyed by 
a temperature of 80° C. for one hour. Aside from 
its occurrence in meat, nothing is known of the life 
history of the bacillus. 

The disease is caused by the toxin which has al- Toxin. 
ready been produced in the meat and not by the 
activity of the organism after it has reached the 
alimentary tract (v. Ermengem). If an extract 
of the meat is made with water and the bacteria 
removed from the latter by filtration, the fluid 
shows characteristic toxicity for animals. This 
experiment may be used for determining the pres- 
ence of botulism toxin in suspected meat. The 
guinea-pig is the most susceptible animal. 

1. Other pathogenic organisms, especially B. cntcritirfis 
and B. coli communis, and recently the paratyphoid bacil- 
lus, have been found in poisonous meats. The term 
botulism formerly was applied to various forms of meat 
poisoning. 



258 INFECTION AND IMMUNITY. 

According to v. Ermengem, the bacillus does not 
proliferate in the body, nor does it produce toxin 
vigorously at body temperature; hence, he consid- 
ers it to be a strict saprophyte — a pathogenic sap- 
rophyte. 

The toxin is taken up by the circulation from 
the alimentary tract and is not destro}-ed by the 
gastric and pancreatic juices, differing in this re- 
spect from the toxins of diphtheria and tetanus. 
It is prepared artificially by growing the organism 
anaerobically in suitable bouillon and subsequently 
sterilizing the fluid by filtration. Like the other 
soluble bacterial toxins, it is susceptible to the ac- 
tion of air and light, and is destroyed bv a tem- 
perature of from 60 to 70° C. 
Pathogenesis. That the toxin has a special affinity for the nerv- 
ous tissues is evident from the symptoms of the 
disease; histologically, the ganglionic cells show 
degeneration in fatal cases. Further evidence of a 
strong affinity between the toxin and nervous tissue 
lies in the ability of the latter to neutralize the 
toxin in the test-glass. The toxin, however, ap- 
pears not to be so selective in its action on the 
nervous tissue as the toxin of tetanus, for in bot- 
ulism degenerations of the glandular organs, and 
of the vascular endothelium with consequent hem- 
orrhages are characteristic anatomic findings. 
Man appears to be very susceptible to the intoxica- 
tion, whereas dogs, rats, and cats are relatively im- 
mune. The toxin is pathogenic by subcutaneous or 
intravascular injection. 

Acording to v. Ermengem, the bacilli when in- 
oculated subcutaneously do not proliferate, but are 
taken up by the phagocytes immediately or after 
thev have been carried to other organs. Animals 



PYOCYAXEUS. 250 

which have recovered from infection or which have 
been immunized acquire rather strong immunity 
to subsequent inoculations, the immunity being 
antitoxic. 

The prophylactic measures consist in the avoid- prophylaxis 
ance of poorly preserved and improperly cooked andAnt,lox ' 
meats, especially sausages. Botulism would seem 
to be very rare in this country where raw meats 
are not used extensively. 

The antitoxin (Kempner) has proved of some 
value in animal experiments, but its commercial 
preparation has not been warranted on account of 
the rarity of the disease. 

IV. BACILLUS PYOCYAXEUS. 

For a long time it was thought that the "bacillus Pathogenic 
of blue pus" was of no importance as an infectious 
agent for man, although its pathogenicity for ani- 
mals had been recognized experimentally. It is 
found with some frequency in the blood and or- 
gans of man at autopsy, when death has resulted 
from some other infection or chronic disease, and 
in such instances it is supposed that a so-called 
"agonal invasion" by the organism has occurred. 
During recent years, however, several cases of pri- 
mary pyocyaneus septicemia have been observed, 
the bacillus having been obtained from the blood 
in pure cultures during life or from the blood and 
organs shortly after death. It has been found as 
the sole organism in meningitis and vegetative en- 
docarditis. Some of the cases indicate, however, 
that a previous lowering of resistance, as that 
caused by tuberculosis and s} T philis, is important 
for general invasion by the bacillus. It has been 
found several times in suppurative processes in the 
middle ear, and would seem to be either the cause 



260 



INFECTION AND IMMUNITY. 



Its Manifold 
Activities. 



or a strong adjuvant in some cases of severe enter- 
itis, especially in childern. In systemic infec- 
tions, the symptoms are typhoidal in character, 
with high temperature, diarrhea and a tendency 
to the formation of hemorrhages in the skin and 
internal organs. 

The Bacillus pyocyaneus is widely distributed 
and that it causes so few infections is probably due 
to its low pathogenic power. It is an organism of 
manifold activities. It produces a substance, pyo- 
cyanin, which, when exposed to the air, assumes a 
bluish tint, and on which the color of the pus de- 
pends; pyocyanin is soluble in chloroform., from 
which it may be precipitated in crystalline form. 
Under proper conditions the organism also forms 
Ferments, a fluorescent pigment. It produces a strong pep- 
tonizing ferment, coagulates milk, and in old 
cultures an autolytic ferment is found which di- 
gests many of the bacilli. As stated in a previous 
chapter, Emmerich and Lowe have identified a 
bacteriolytic ferment, pyocyanase, which dissolves 
the anthrax bacillus and other organisms. The 
ferment nature of this substance is in some doubt, 
inasmuch as it resists the boiling temperature. 
Dietrich thinks its action is due to the production 
of osmotic changes. Old cultures contain a hemo- 
lytic agent (pyocyanolysin) of an alkaline nature, 
which resists boiling and is not a true toxin, since 
immunization with it does not yield an antitoxin 
(Jordan). In addition to the products mentioned, 
the organism secretes a true soluble toxin for 
which it is possible to obtain an antitoxin, and 
possesses, furthermore, an endotoxin for which 
an antitoxin can not be obtained. 

The soluble toxin of Bacillus pyocyaneus is not 



Toxin and 
Endotoxin. 



PYOCYAXEUS. 



261 



produced in large amounts. It differs from the 
other soluble toxins in its resistance to heat, with- 
standing a temperature of 100° C. for fixe min- 
utes. It produces the symptoms which are char- 
acteristic of infection with the living organism, 
the principal anatomic changes being parenchyma- 
tous degenerations and ecchymoses, the latter sup- 
posedly being due to degenerative changes in the 
endothelium of the vessels. 

By immunizing with young cultures grown on Antito ^ and 
an agar surface a serum which is purely bacterid- |jJJms Cidal 
dal is obtained. On the other hand, if an older 
toxin-containing bouillon culture be used, the 
serum is both bactericidal and antitoxic. The 
serum which is purely bactericidal has no power of 
neutralizing the toxin. The toxin solution con- 
tains not only the true toxin, but also quantities 
of endotoxin which were liberated as the dead 
bacilli were dissolved. Inasmuch as the antitoxin 
neutralizes only the true toxin, leaving the endo- 
toxin unbound, the toxicity of the filtrate can not 
be destroyed entirely by antitoxin, a condition 
which is brought out clearly when the attempt is 
made to neutralize a multiple of the simple fatal 
dose by the corresponding amount of antitoxin. 
In such multiples a fatal amount of endotoxin is 
present. Although a strong antitoxin may be ob- 
tained, it would appear to be of little practical 
importance because of the rarity of infections by 
the bacillus. 

Infection in man has caused the formation of 
agglutinin in several instances, but it has been 
absent in others. An agglutinating serum is read- 
ily produced by artificial immunization. 



Agglutination. 



262 INFECTION AND IMMUNITY. 

V. OTHER SOLUBLE BACTERIAL TOXINS. 

Soluble toxins, of perhaps secondary impor- 
tance, which are produced by the staphylococcus 
and streptococcus, will be considered in the sections 
dealing with these organisms. It seems probable 
that they do not represent the essential toxic 
agents of the cocci, but rather that the toxicity of 
the latter depends chiefly on the action of endo- 
toxins. 

B. INTOXICATION BY SOLUBLE PLANT TOXINS. 
I. HAY FEVER. 

Dunbar separated from the pollen of various 
grains a toxin which is able to precipitate typical 
attacks of hay fever in those who are susceptible, 
having first demonstrated that the crude pollens 
cause the disease. The pollen from the following 
are said to contain the toxin : Eye, barley, wheat, 
maize (corn), dog's tail, couch-grass, millet, rice 
and some others. The so-called autumn-catarrh 
which is common in America may be due to a 
slightly different toxin coming from the golden- 
rod, rag-weed, and perhaps other autumnal flower- 
ing grains. 
The Toxin. The toxin usually is associated with certain 
starch-like granules which are contained in the 
pollen, but it occurs also in pollens which do not 
contain these granules. It may be extracted with 
water or salt solution, is precipitated by alcohol, 
resists the boiling temperature, and is of an al- 
buminous nature. 
Pathogenesis. When the crude pollen reaches the conjunctiva, 
nasal or bronchial mucous membranes, the toxin 
is dissolved out by the secretions and absorbed by 
the lymphatics. When applied to the conjunctiva 



Pollantin. 



HAY FEVER. 263 

it causes swelling, redness and lachrymation. It 
is carried by the tears to the nose and here causes 
excessive secretion, swelling of the mucous mem- 
brane and sneezing. It may become distributed 
systemically as a result of absorption from the 
free surfaces and cause the asthmatic attacks and 
general s}mrptoms which are seen in the intoxica- 
tion. When injected subcutaneously into the arm 
both the asthmatic attacks and coryza-like symp- 
toms were produced. 

Dunbar's antitoxic serum (pollantin) is ob- Antitoxic Serum 
tained by immunizing horses with the toxin. It 
seems to be of undoubted value in a certain per- 
centage of cases, but fails unaccountably at times. 
It is, perhaps, most effective when used in the 
prodromal stage, the attacks being thereby pre- 
vented. Its failure in certain instances may be 
due in part to the inefhcacy of the antitoxin 
against the toxins of certain pollens. Again, in 
certain individuals the affinity of the toxin for 
the tissues may be unusually great so that a more 
vigorous use of the remedy is demanded. 

Ltibbart and Prausnitz published statistics of 
285 cases, of which 65 were autumnal. In ordi- 
nary hay-fever the serum gave positive results in 
57 per cent., partially positive in 32 per cent, and 
negative results in 11 per cent, of the cases. In 
autumnal catarrh, 70 per cent, were positive, 19 
per cent, partially positive, and 11 per cent, nega- 
tive. 

The small bottles of antitoxin are accompanied 
by a pipette with which from one to several drops 
may be instilled into the eye or the nose. 



264 INFECTION AND IMMUNITY. 

The serum does not cure permanently and one 
who is susceptible should carry a vial for imme- 
diate use during the hay-fever season. 

II. OTHER PLANT TOXINS. 

Kicin, from the seeds of Ricinus communis; 
abrin, from Abrus precatorius; crotin from the 
seeds of Croton tiglium; and robin, from the leaves 
and bark of the locust tree (Rohinia pseudoacacia) 
are chiefly of experimental interest. They are 
similar in their action, are very toxic to animals, 
producing both local and general changes with 
fatal termination when given in sufficient doses ; 
they have pronounced agglutinating action on the 
erythrocytes of most animals, and in some in- 
stances are slightly hemolytic. By guarded im- 
munization antitoxins may be obtained for them. 

Kobert gave the name of phallin to a toxic sub- 
stance which may be extracted from poisonous 
mushrooms, particularly the "Deadly Amanite" 
(Amanita phalloides) . In some countries many 
deaths are caused by eating this variety: Bussia, 
Germany, Italy, France, Japan (Ford). Phallin 
is very toxic for animals and is strongly hemolytic 
for many bloods. By immunization Ford has re- 
cently obtained an antitoxin which neutralizes the 
hemolytic action of the poison, and which in a dose 
of 0.5 c.c. protects rabbits against five fatal doses 
of the toxin. The toxin is an aqueous extract of 
the dried plants. 

C. INTOXICATION BY SOLUBLE ANIMAL TOXINS. 
I. POISONING BY SNAKE BITES. 

The poison apparatus of snakes consists of a se- 
cretory gland on each side which communicates 
with a tubular fang by means of a duct. In the 



SNAKE YEXOU. 265 

passive state the fangs are directed backward on Toxic 
the roof of the month, bnt when the animal strikes 
their points are made to project forward and the 
poison is forced throngh the canals by mnscnlar 
compression of the sac. The venom is a glandular 
secretion. 

The venoms of different snakes vary a great 
deal in their toxic properties. The most impor- 
tant constitnents are those which attack the nerv- 
ons system (neurotoxin), the blood corpuscles 
(hemolysins and hemagglutinins) and the endo- 
thelium of the blood vessels, causing hemorrhages 
(hemorrhagin, an endotheliotoxin). The three are 
independent. 

The neurotoxin causes death by paralysis of the 
cardiac and respiratory centers. The hemolysin 
appears to be of less importance as a cause of 
death. 

The venoms of the cobra, water-moccasin, da- variations in 
boia and some poisonous sea-snakes are essentially ties and°cy e - r " 
neurotoxic, although they have strong dissolving 
powers for the erythrocytes of some animals. In 
studying the hemolytic powers of the venoms of 
cobra, copperhead and rattlesnake, Flexner and 
ISToguchi found cobra venom to be the most hemo- 
lytic and that of the rattlesnake the least. They 
attribute the toxicity of rattlesnake poison chiefly 
to the action of hemorrhagin. The same authors 
studied the action of different venoms on the cells 
of various animals and by absorption experiments 
found independent cytotoxins for the testis, liver, 
kidney and blood. Not only was there a distinct 
cytotoxin for each organ of an animal, but also 
for the same organ of different animals, results 
which speak for a remarkable complexity of 



totoxins. 



266 INFECTION AND IMMUNITY. 

venom. Certain venoms contain a leucocytic 
toxin. 
Ferments. That venoms contain proteolytic ferments is 
shown by their ability to digest gelatin and fibrin. 
This power may be related to the softening of the 
muscles which has been noted clinically in cases of 
poisoning. The rapid decomposition of the body 
which follows death by snake-poisoning is asso- 
ciated with a decrease in the bactericidal power of 
the blood, which, according to Flexner and No- 
guchi depends on fixation of the complement by 
the venom. 
Amboceptors The hemolysin and neurotoxin, and perhaps 
°ment. other cytolysins of venom, consist of amboceptors 
which in themselves are non-toxic; they become 
toxic only through the aid of complements which 
are present in the body of the poisoned animal. 
In this instance, complement which usually is a 
source of protection becomes a source of danger to 
the animal possessing it. Not only does ordinary 
serum-complement serve for activation, but Kyes 
discovered that cells (er}i:hrocytes) may contain 
another kind of complement, an "endocomple- 
ment," which activates the amboceptors after the 
latter have combined with the cells. Flexner and 
ISToguchi found that this also was the case with 
the neurotoxic amboceptors. 

The ability of lecithin to activate the hemolytic 
amboceptors of cobra venom and the preparation 
of cobra-lecithid (Kyes) were described in Part I, 
Chapter XII, pages 158-160. In the preparation of 
cobra-lecithid the neurotoxin is separated from 
the hemolysin, the former remaining in solution, 
whereas the latter settles as a precipitate in com- 
bination with the lecithin. Immunization with 



SNAKE VENOM. 267 

the neurotoxin isolated in this way causes the for- 
mation of a specific antineurotoxin (Elliot). The 
neurotoxin may also be abstracted from the venom ■ 
by treating the latter with the nervous tissue of a 
susceptible animal (Flexner and Noguchi). 

The hemolysin is distinct from the hemagglu- 
tinin and the latter may be eliminated by heating 
the venom to from 75° to 80° C. In the action of 
venom on erythrocytes agglutination precedes he- 
molysis. 

The toxins may be converted into toxoids by Toxoids and 
heat or treatment with chemicals. Immunization 
with toxoids causes the formation of antitoxins. 
Eadium is said to destroy the toxicity of venom 
(Physalix). 

The antivenin of Calmette is obtained by im- 
munizing horses with a mixture of venoms (80 
per cent, cobra, 20 per cent, viperine venom) which 
are attenuated before injection. Six months are 
required to produce a strong serum. The claim 
of Calmette that his serum is effective against all 
snake-venoms is erroneous. It neutralizes those 
venoms the toxicity of which depends largely on 
neurotoxins and hemolysins, but has little influ- 
ence on rattlesnake poison, the essential toxin of 
which is hemorrhagin. Antivenin for the rattle- 
snake and water-moccasin may be prepared by im- 
munization with the corresponding venoms which 
have been attenuated by weak acids. Noguchi has 
produced serum of such strength that it promises 
to be of practical value in the treatment of rattle- 
snake bites. 

As indicated previously, the action of venom is 
preceded by no appreciable incubation period; 
hence, an antitoxin to be effective must be admin- 



268 INFECTION AND IMMUNITY. 

istered not later than a few hours after the bite 
has occurred. Noguchi found in relation to anti- 
venin for the rattlesnake that the antitoxin neces- 
sary to save was quadrupled three hours after in- 
travenous injection of two fatal doses of venom. 
Fortunately the venom is less toxic when intro- 
duced subcutaneously. 

II. OTHER ZOOTOXINS. 

Phrynolysin, which is present in the blood and 
skin of certain toads, has been studied especially 
by Proscher. It is a thermolabile, hemolytic toxin 
for which an antitoxin can be obtained by immuni- 
zation. 

Arachnolysin, obtained from the bodies of cer- 
tain spiders, is a hemolytic toxin, which by immun- 
ization yields a specific antitoxin. 

A poison, with properties resembling those of 
snake venom, may be obtained from the caudal 
segment of the scorpion. Antitoxin is produced 
by immunization. 

Ichthyotoxin, a name given to the toxic proper- 
ties of eel serum, is composed of a neurotoxic and 
a hemotoxic constituent. 

From the poisonous glands of certain fish 
(Trachinus draco) a highly toxic, thermolabile 
substance is obtainable, for which an antitoxin can 
be prepared by the immunization of rabbits. 



GKOUP II. 



Acute infectious diseases caused by bacteria 
which do not secrete strong soluble toxins in cul- 
ture media, but which contain endotoxins (toxic 
protoplasm). Infection or immunization causes 
immunity of considerable or prolonged duration. 
In active immunity the serums agglutinate the 
corresponding organisms and are protective for 
other animals,* but have little or no curative 
power. The formation of antitoxins is not defi- 
nitely established. In most instances vaccination 
has been accomplished. Clinically there is leuco- 
cytosis in some instances and hypoleucocytosis in 
others (typhoid and Malta fever). 

A. The serum in acquired immunity is bactericidal. 

I. TYPHOID FEVER. 

Eberth first saw Bacillus typhosus in micro- 
scopic preparations of the mesenteric lymph glands 
and spleen of a typhoid corpse, in 1880. Koch 
also observed it at about the same time, and 
stained it in the intestinal wall, spleen, liver and 
kidney. It was obtained in pure culture by Gaffky 
in 1884. 

The organism is rod-shaped, 0.5 to 0.8 by from 
1 to 3 microns in dimensions, with nothing char- 
acteristic in its morphology. It possesses from ten 
to twelve flagellae situated at the end and on the 
sides and is actively motile under suitable condi- 
tions. It forms no spores and is readily cultivated 
on many media. 

The bacillus is one of the rather numerous "in- 

* This has not been established in regard to Malta fever. 



270 INFECTION AMD IMMUNITY. 

testinal group" of organisms, certain members of 
which are so similar that they can be differentiated 
only by means of special culture manipulations, 
animal experiments, or the agglutinating and bac- 
tericidal action of specific immune serums. 1 
Distribution of The organism has been cultivated from earth 
and infected water, and from the feces, urine, 
blood, rose-spots and the various organs of typhoid 
patients. In many instances in which an epidemic 
has certainly been caused by an infected water sup- 
ply attempts to cultivate the bacillus from the 
water have failed. The organisms may not have 
been included in the samples which were analyzed, 
or, what is equally probable in certain instances, 
they have died out in the water by the time the 
disease was so widespread as to be considered epi- 
demic. Its occurrence in nature depends on the 
distribution of the infected excretions of the dis- 
viabijityand eased. The viability and virulence of the bacillus 
in water, earth, etc., vary with the nature of 
its surroundings. It has been found to live 
for periods of from 2 to 4 weeks to 2 or 3 
months in water, from 3 to 4 months in milk, 
from 3 to 5 months in surface water, and from 
11 to 16 months in sterilized earth; 100 days 
in ice, from 12 to 30 days in oysters, from 50 to 
80 days when dried on clothing, for 3 months in 
typhoid feces, for 96 days in the dead body of an 
experiment animal. When in water or moist earth 
which contain many saprophytes its life is short- 
ened. It survives drying for many months, al- 

1. Of this group the bacillus of dysentery, paratyphoid 
bacillus, Bacillus cntcritidis of Gartner, colon bacillus and 
Bacillus alcaligencs, in addition to the typhoid bacillus, are 
the most important because of their similar' morphologic and 
cultural properties and the pathogenicity of certain of them. 



TYPHOID FEVER. 



271 



Typhoid 
Epidemics. 



though direct sunlight kills in the course of a few 
hours. 

The typhoid bacillus secretes no soluble toxin, Endotoxin 
but contains an endotoxin which may be obtained 
in solution by the autolytic digestion of cultures, 
by extracting ground-up bacilli or by squeezing out 
the plasma under high pressure. Up to the pres- 
ent time, immunization with none of these prepa- 
rations has resulted in the production of an anti- 
toxic serum of accepted value. 

Typhoid fever may become epidemic either 
through a contaminated water supply or by contact 
infection. When due to infected water there is 
something characteristic about the explosive-like 
suddenness with which dozens or even hundreds 
are stricken within a short period. The water of 
streams, small lakes or reservoirs may become in- 
fected from an ill-constructed out -house, or from 
discharges which have been thrown on the ground 
in their vicinity. Typhoid stools thrown on the 
ground adjacent to wells have caused miniature 
epidemics. Fruit, vegetables and milk cans may 
be infected by washing them with contaminated 
water, and it is supposed that the disease may be 
acquired from oysters which have lain in water 
contaminated with sewage. 

By whatever means an epidemic is set in motion, 
primarily, it is usually aggravated and prolonged 
by the occurrence of contact infections (indirect 
contact). The hands of the nurse, physician, or 
others who come in contact with the patient be- 
come contaminated from the stools, urine, soiled 
linen or skin of the patient, and the organisms 
subsequently are transferred to food, drinking 
water, or in other accidental ways reach the mouth. 



272 INFECTION AMD IMMUNITY. 

Each new case is a fresh focus from which infec- 
tion may be carried to others, and the chances of 
milk and food infection become greater as the 
cases multiply. When the discharges are not dis- 
infected or are improperly disposed of, soil or 
house infection may occur and the possibility 
of transmission by germ-laden dust becomes of 
importance. Dust infection from dried urine 
or feces and drop infection from urine, water, 
or the sputum of the patient are theoretical- 
ly possible, but would seem to be of minor sig- 
nificance. That flies may carry the organisms 
from open vaults or cesspools and deposit them on 
food or in drinking water has been appreciated in 
relation to epidemics in military camps. Typhoid 
bacilli have been cultivated from flies which were 
taken from the vicinity of infected material. 
The infection The micro-organisms gain access to the body 
through the lymphoid tissue of the intestinal tract 
(Peyer's patches and the solitary follicles). The 
occurrence of primary infection of the lungs 
through inhalation of infected dust is possible, but 
has not been definitely proved. In this instance 
typhoid bacillemia might occur either with or 
without intestinal infection. In the latter case it 
would seem essential that some local lesion exist 
in the lungs or elsewhere from which organisms 
could constantly be supplied to the blood. Neufeld 
doubts the ability of the typhoid bacillus to pro- 
liferate in the blood, because of the strong bacteri- 
cidal power of the latter, and considers that infec- 
tion takes place through the intestines even in cases 
of "typhoid without intestinal lesions." 
incubation The incubation period is subject to considerable 
variations. In a series of cases in which the date 



Atrium. 



Period 



TYPHOID FEVER. 273 

of exposure was known, 62 per cent, showed s}TQp- 
toms in from 20 to 25 days, 2 per cent, in from 14 
to 20 days, and 2 per cent, later than 30 days. 

Following the development of intestinal lesions, Localization 
the bacilli reach the circulation by way of the lym- 
phatics, and through the action of the bactericidal 
constituents of the blood (amboceptor-complement 
complex and possibly leucocytes) they are killed 
and dissolved in large quantities. It is now gen- 
erally believed that only through the disintegra- 
tion of the bacterial cells are their toxic constitu- 
ents thrown into solution in the body, a condition 
which is necessar}^ in order that the tissues be in- 
jured. Infection of the blood stream with living 
organisms, in the early stages of the disease and 
preceding relapses, occurs in a large percentage of 
the cases. 

It is possible to establish the diagnosis Of Diagnosis by 

typhoid fever by cultivating the bacilli from the B,ood Cultures * 
blood, even before the serum has developed suffi- 
cient agglutinating power to give a positive Widal 
reaction. A small flask of bouillon is inoculated 
with from 1 to 5 c.c. of blood, drawn from the 
median vein of the arm, and after twenty-four 
hours of incubation a small portion of it is plated 
out. Colonies which devlop on the plates may be 
identified by the usual bacteriologic methods, or 
the agglutination test may be performed with a 
known antityphoid serum. After from the tenth 
to the fourteenth day the organisms can rarely be 
cultivated from the blood; the bactericidal sub- 
stances of the blood may have so increased by this 
time that circulating bacilli are killed rapidly. 

In from one-fourth to one-third of the cases, in 
the third week, or during convalescence, the bacilli 



274 INFECTION AND IMMUNITY. 

appear in large numbers in the urine, in which 
they may persist for many weeks. According to 
Kanjajeff, they are discharged into the urine from 
metastatic foci in the kidneys. 

Many of the symptoms, complications and se- 
quelae of typhoid fever, as the rose-spots, enlarged 
spleen, bone lesions, and. in some instances nervous 
.lesions and pneumonia, depend on the distribution 
of the bacilli. This is in contrast to the conditions 
in diphtheria and tetanus, in which the distribu- 
tion of the bacilli is of little significance for the 
involvement of particular organs. The anatomic 
changes and clinical symptoms suggest that the 
lymphoid tissue and central nervous system have 
a special affinity for the toxic constituents of the 
typhoid bacilli. 
Endothelial The greatest changes take place in the organs 
Hyperplasia, (lymphoid) which contain the bacilli most con- 
stantly and in the greatest numbers. It is here 
that the toxic substance may be present in greatest 
concentration, as a consequence of the continual 
solution of the organisms. Mallory describes an 
enormous hyperplasia of the endothelial cells, es- 
pecially those of the lymphatic structures. The 
•cells are phagocytic, and especially in the lymphoid 
tissue of the intestines and in the mesenteric 
lymph glands, englobe and destroy the lymphoid 
cells on a large scale. It seems probable that the 
endothelial proliferation which has been described 
is due to the rather mild but prolonged action of 
the dissolved toxic constituents of the typhoid ba- 
cillus; the condition is that of an inflammatory 
hyperplasia. It has been suggested that the hypo- 
leucocytosis of typhoid fever is due to the destruc- 
tion of the lymphocytes in the lymphoid organs by 
the endothelial phagocytes. 



TYPHOID FEVER. 275 

The granular and fatty degenerations of the 
parenchymatous organs do not differ from those 
seen in many acute infections. 

The conditions in the intestinal tract would Mixed 
seem to favor mixed infections, especially by the ,nfect,ons - 
colon bacillus and streptococcus, and the primary 
infection probably decreases the resistance to sec- 
ondary invasion. The role of the colon bacillus in 
typhoid fever is perhaps not definitely established, 
although it has been found in the circulation, in 
abscesses, and in the urine in cases of cystitis ac- 
companying the disease. The typhoid and colon 
bacilli grow well together. A mixed general in- 
fection with the streptococcus causes a grave sep- 
tic condition characterized by an irregular tem- 
perature curve. This condition may be discovered 
by blood cultures. It is thought that the strepto- 
coccus does not increase the toxicity of the typhoid 
bacillus, the result being rather a summation of 
the intoxication of the two infections. Post- 
typhoidal suppurations are often due to the strep- 
tococcus and in many of the metastatic complica- 
tions (parotitis, pleurisy, peritonitis, meningitis, 
otitis media) streptococci and staphylococci have 
been found. Pneumococcus pneumonia not infre- 
quently complicates typhoid fever. A combined 
infection of typhoid and malaria is said to occur in 
the tropics; the complication is grave. Typhoid 
and diphtheria may occur together, and typhoid 
may be superimposed on acute tuberculosis. 

The period of greatest susceptibilitv to tvphoid immunity and 
is found from the fifteenth to the twenty-fifth Susceptibility. 
years. The resistance of infants and children is 
imt satisfactorily explained. A certain amount of 
resistance inherited from the mother may persist 



276 INFECTION AND IMMUNITY. 

for some years after birth. It is known that anti- 
bodies may pass from the mother to the fetus 
through the placenta. In very early life the tissues 
may respond more energetically to incipient in- 
fection by the rapid formation of typhoid anti- 
bodies, or the phagocytic cells may be more active. 
The conditions which render older people less sus- 
ceptible are no better understood. A loss of suit- 
able receptors may have occurred so that the toxic 
constituents of the bacilli find no anchorage in the 
body, or the affinity between the receptors and the 
toxic constituents may have become less. The in- 
dividual during the course of years may have been 
gradually immunized by the entrance of non- 
pathogenic quantities of the bacilli into the cir- 
culation. That resistance to typhoid infection is 
decreased by low nutrition and overwork is a long- 
known fact. 

Natural and A large amount of protection is afforded by the 
munity. hydrochloric acid of the gastric juice, and it is 
reasonable to believe that suppression or an insuf- 
ficient amount of hydrochloric acid may favor the 
passage of living bacilli to the intestines. Normal 
human serum is rather strongly bactericidal for 
the typhoid bacillus, and the leucocytes ingest and 
destroy it. Metchnikoff ascribes natural immun- 
ity to the action of the microphages. 

Duration of The immunity which follows an attack of 
typhoid fever is generally of long duration, but 
second attacks occur with some frequency. It has 
been noted that limited communities which have 
experienced an epidemic may remain relatively 
free from the disease over a period of some years, 
although neighboring districts are attacked. All 
the susceptible persons having had the disease, a 



Acquired 
Immunity. 



TYPHOID FEVER. 277 

state of temporal regional immunity is created. 
Acquired immunity is characterized by an increase 
of the bactericidal amboceptors, agglutinins and 
typhoid precipitins in the serum. It is com- 
monly believed that recovery is due to the increase 
of the bactericidal power of the body fluids, which 
becomes most marked during the later period of 
the disease or during convalescence. It seems cer- 
tain, however, that the new resistance persists be- 
yond the time when the bactericidal power of the 
serum has returned to normal, which may take 
place in from one to several years. The bacteri- 
cidal power sinks rapidly during and following 
convalescence. However, the general principle is 
well established that, although the antibodies may 
have disappeared entirely, they are reformed more 
readily as a consequence of an old infection (Neis- 
ser and Shiga). The tissue cells have, so to say, 
been trained, and are stimulated by a few micro- 
organisms to produce such a quantity of bacteri- 
cidal amboceptors that the incipient infection is 
overcome. It is, of course, understood that the 
amboceptors require the aid of complement in kill- 
ing the micro-organisms. A second attack of 
typhoid fever usually is mild. 

MetchnikofJ does not deny that the amboceptors 
(fixators) play an important part in acquired im- 
munity, but claims that the new resistance de- 
pends chiefly on an increase in the phagocytic 
power of the microphages (polymorphonuclear leu- 
cocytes). This is not clear from the clinical 
standpoint because of the hypoleucocytosis which 
is somewhat characteristic of typhoid — a hypoleu- 
cocytosis caused chiefly by a disappearance of the 
microphages. It has been suggested that our con- 



Leucocytes. 



278 INFECTION AND IMMUNITY. 

elusions as to hypoleucocytosis are based on ex- 
amination of the peripheral blood, whereas the 
mesenteric vessels may show hyperleucocytosis. 
Mallory, however, found a striking absence of 
microphages even in the intestinal vessels. Con- 
cerning a theory that the hyperplasia of the lym- 
phoid organs serves as a substitute for the hyper- 
leucocytosis, we may recall the findings of Mallory 
that this hyperplasia is chiefly one of endothelial 
cells. The importance of these endothelial cells 
for the destruction of typhoid bacilli needs further 
investigation. 
Prophylaxis. Prophylaxis should begin with the thorough 
disinfection of the stools and urine of typhoid pa- 
tients, and this should be continued until they no 
longer contain typhoid bacilli. It is not good 
hygiene to discharge a patient until bacteriologic 
examination of stools and urine show them to be 
free from the organisms. It would be difficult to 
carry out this rigid precaution under all condi- 
tions, but at all events the stools and urine may be 
disinfected for a reasonable period, say through- 
out convalescence. There is no sufficient reason 
for the neglect of the bacteriologic examination in 
hospital practice. There is a growing sentiment 
that typhoid patients in hospitals should be iso- 
lated in wards or rooms in which there is a fixed 
routine for the disposal of infectious materials — 
urine, stools and sputum. Soiled linen, the bath 
water of typhoid patients, the remnants of food 
and drink, and the eating utensils should be dis- 
infected before removal from the room. Nurses 
or attendants should not eat or drink in typhoid 
rooms. 



TYPHOID FEVER. 



279 



The value of hexamethylenamine in causing the Hexamethyl- 
disappearance of bacilli from the urine is now well enamme - 
known, and the advisability of using the drug as 
a routine measure for public safety is worthy of 
consideration. The room should be kept free from 
flies and eventually it should be disinfected, pref- 
erably by formalin. During an epidemic, in case 
the water supply of a community is susceptible to 
contamination ,all water used for drinking, wash- 
ing of vegetables and eating utensils, should be 
boiled, and that used for general cleaning may be 
otherwise disinfected. The possibility of dust in- 
fection of a house should not be disregarded. 

There are two methods of specific prophylaxis serum Therapy 
against typhoid: 1, the injection of antityphoid ?jo d n . Vaccma ' 
immune serum; 2, preventive inoculation with 
killed cultures of the bacilli. Antityphoid serum 
confers a fairly strong and immediate immunity 
which, however, is of short duration, because of 
the rapid elimination of the serum. Its use as a 
general preventive, therefore, is not advocated. 

Wright has been influential in showing the util- Wright's 
ity of protective inoculations against typhoid. His and h Resuits. 
first experimental work was published in 1896. 
Since that time the inoculations have been carried 
on extensively in British regiments in India and 
South Africa. The occurrence of typhoid among 
the inoculated was one-half that among the unin- 
oculated, and the inoculations reduced the mor- 
tality of the disease by one-half. The protection, 
so far as known, lasts for two or more years, al- 
though in some instances infection has occurred in 
from three to six months after vaccination. 

The methods of preparation of the vaccine are The vaccine. 
elaborate in order to insure sterility and standard- 



280 INFECTION AND IMMUNITY. 

ization. Cultures of the bacillus are grown in 
bouillon for from twenty-four to forty-eight 
hours, and then sterilized at 60 C. The contents 
of several flasks are mixed in order to obtain a 
uniform distribution of organisms, and standard- 
ization is then accomplished by a convenient meth- 
od of estimating the number of bacilli in a cubic 
centimeter of the vaccine. The purity of the vac- 
cine is insured by hacteriologic tests, and for. pres- 
ervation carbolic acid or lysol is added. 
Effects. Wright has abandoned his original method of 
giving a single injection and now recommends two 
moderate doses, which are given from eight to 
fourteen days apart. The first dose includes a 
quantity of vaccine which contains from 750,000,- 
000 to 1,000,000,000 of bacilli, the second 1,500,- 
000,000 to 2,000,000,000. Wright finds that "the 
inoculation of these quanta induces an ample 
elaboration of antitropic substances (antibodies) 
without producing any severe constitutional reac- 
tion." The inoculations increase the bactericidal 
and agglutinating powers of the serum and it is 
concluded that an increased resistance to typhoid 
intoxication is established because the second in- 
jection causes milder symptoms than the first. 
The phagocytic power of the leucocytes is raised, 
because of an increase in the "opsonic antitropins" 
(Part I, Chapter XIY). The curve of the anti- 
bodies is like that usually obtained by active im- 
munization with bacteria, toxins or other sub- 
stances. Immediately following the inoculation 
there is a decrease even of normal antibodies. This 
"negative phase" lasts for from one to several days 
and corresponds to a period of increased suscepti- 
bility. It is quickly followed by a positive phase 






TYPHOID FEVER. 281 

in which the antibodies and, correspondingly, the 
resistance increase rapidly. "When very small 
doses are administered the positive phase may be 
recognized after twenty-four hours (Wright). 
Large doses cause a prolonged negative phase and 
are to be avoided. 

Following injection, "the local symptoms first Local 
make themselves felt after an interval of two or eact,ons - 
three hours. The effects then seen are the develop- 
ment of a red blush and more or less serous exuda- 
tion at the site of inoculation, followed by some 
lymphangitis along the lymphatics which lead, ac- 
cording as the vaccine has been inoculated above 
or below the middle line of the trunk, in the direc- 
tion of the glands of the axillae or of the groin. 
. . . Even severe inflammation has never led on 
to suppuration." The exudate is somewhat hem- 
orrhagic, and the pain moderate to severe, but not 
of long duration. With the technic as recom- 
mended at present, "the constitutional symptoms General 
are limited to some headache and to two or three React,on - 
hours of real malaise. . . . The next day his 
temperature comes down to normal, and he feels 
comparatively well except in respect to pain at the 
seat of inoculation." 

The adoption of antityphoid inoculation or vac- conditions for 

,. •, , . -,.,. i Vaccination. 

cmation under certain conditions appears to be 
warranted. Typhoid never has been a world pest ; 
hence, the occasion for universal vaccination does 
not exist, but in the presence of epidemics so fre- 
quently seen in American cities it will be impos- 
sible to avoid the consideration of vaccination as a 
means of protecting the uninfected. The question 
is a pertinent one also for those cities in which 
typhoid is so extensive as to be called endemic. 



282 INFECTION AND IMMUNITY. 

Mixed Active It has been suggested that the "negative phase" 

and Passive , ., , , . „ -. . , , x 

immunization, described above is a source of danger in the pres- 
ence of an epidemic. The phase is so short, how- 
ever, that the danger is minimal and it seems 
probable that the practice of mixed active and 
passive immunization would eliminate it entirely. 
This is accomplished by the combined injection of 
antityphoid* serum and vaccine. The serum as- 
sures a positive phase from the start, and before 
this has subsided, that induced by the vaccine is 
established. When specific serum is mixed with 
the vaccine the local reaction is said to be less 
severe. 

The products of autodigestion of typhoid cul- 
tures have been suggested as suitable vaccine 
(Neisser and Shiga). The local reaction is said 
to be mild, and the body reacts by the formation 
of bactericidal amboceptors and agglutinins. 
Serum Bactericidal serums obtained by the immuniza- 
Therapy. ^ on f h orses w ith typhoid bacilli have not shown 
distinct curative properties. Chantemesse im- 
munizes horses with a typhoid "toxin" which is 
prepared by growing the organism in a liquid cul- 
ture which contains an emulsion of splenic tissue. 
One cubic centimeter of this toxin will kill a 
guinea-pig, a dose which in comparison with 
other bacterial toxins is very weak. Chantemesse 
has used his antitoxic serum in the treatment of 
more than 500 cases, reporting a mortality of 
about 6 per cent., whereas that among untreated 
patients was from 10 per cent, to 12 per cent. 
Although these figures indicate some value for the 
serum it has had little trial outside of France. 

McFadyan and Eowland immunize horses with 
extracts of typhoid bacilli, which have been ground 



TYPHOID FEVER. 



283 



Preparation 
of Jez. 



up while they were kept in a brittle state by the 
temperature of liquid air. Although antitoxic and 
bactericidal properties are claimed for the serum, 
there is no conclusive evidence that it differs from 
a bactericidal serum prepared in the ordinary way. 

Jez produces a high degree of immunity in rab- 
bits by artificial immunization with the typhoid 
bacillus, then prepares an extract from the spleen, 
bone marrow, brain, etc., of the immunized ani- 
mals. The extract is administered by mouth. Jez 
justifies this method, from the fact that the hrm- 
phoid organs have been shown to form typhoid 
antibodies (TYasserman). From the clinic of 
Eichorst and some others favorable reports con- 
cerning the remedy have been published. It has 
had no extensive use. The preparation is made by 
the Serum Institute of Berne (Switzerland) and 
is expensive. 

The suggestion made by Fraenkel, that typhoid 
patients be treated by subcutaneous injections of 
small quantities of killed typhoid bacilli in order 
to hasten the formation of antibodies has been 
kept alive through the "typhoin" of Petruschky, 
but is yet without much practical trial. Of a simi- 
lar nature is the suggestion of Richardson, that 
the filtrates of typhoid cultures be injected. 

The principles and technic of the agglutination Agglutination 
test were described in Part I. The serum 
commonly becomes agglutinating on from the 
seventh to the tenth day, rarely as early as the 
second or third, and as late as from the twentieth 
to the fortieth day. The power is highest during 
convalescence, when it may agglutinate in dilu- 
tions as high as 1/5,000 or higher, and from 
that time sinks gradually. An agglutinating 



284 INFECTION AND IMMUNITY. 

power of 1/160 has often been found at eight 
months, and of 1/50 after from seven and one-half 
to eleven years; but the latter duration is not the 
rule. In performing the test a serum dilution of 
not less than 1 to 40, or 1 to 50 should be observed 
as previously set forth. 

The following sources of error are to be borne 
in mind: Typhoid fever occasionally runs its 
course without the formation of agglutinins; the 
reaction may mysteriously be absent one day to 
recur a few days later, a condition which indicates 
the importance of repeated tests; rather high ag- 
glutinating power for the typhoid bacillus occa- 
sionally develops in other infections, as pneumo- 
nia, meningitis, icterus, Weir's disease, etc.; the 
possibility of group agglutination, for the positive 
elimination of which control tests with related or- 
ganisms may be demanded. 

In case negative results are obtained in a sus- 
picious case, the reactions should be tried with the 
paratyphoid bacilli. 

The test of the bactericidal powers of the serum 
has been recommended as a substitute for the ag- 
glutination reaction, but the technic is so much 
more complicated that the method will probably 
not come into general use. 

For diagnosis previous to the formation of ag- 
glutinins, blood cultures should be made as de- 
scribed in a preceding paragraph. 

II. PARATYPHOID FEVER. 

Paratyphoid in 1900 Schottmuller cultivated from the blood 
colon" Bacilli, of five "typhoid" patients organisms which differ 
from the typhoid bacillus in that they attack dex- 
trose with gas formation and are not agglutinated 
conspicuously by antityphoid serum. Since that 



PARATYPHOID. 285 

time many similar cases have been reported and 
two types of the paratyphoid bacillus have been 
recognized (Schottmuller). Group B causes first 
an acid reaction in milk which changes to a per- 
manently alkaline reaction in about ten days, 
whereas Group A causes permanent acidity (Kay- 
ser). They resemble the typhoid bacillus morpho- 
logically, but culturally are more closely related to 
to Bacillus enteritidis. Organisms which have 
previously been described as "paracolon" bacilli 
(Widal, Gwyn) do not differ from those which are 
now called paratyphoid bacilli, and the infections 
caused by them resembled the recorded cases of 
paratyphoid fever. The term "paracolon" should 
no longer be applied to them. 

Paratyphoid fever occurs sporadically or in epi- Epidemiology. 
demic form, and bears a close resemblance to mild 
typhoid-like epidemics which have been noted from 
time to time, and which, presumably, are caused 
by eating poisonous meats. One such epidemic of 
600 cases was caused in Switzerland in 1878 by 
the meat of a sick calf; the mortality was 1 per 
cent. A still older epidemic (1839) is cited, like- 
wise caused by meat. In both instances the infec- 
tion eventually was carried from person to person 
by contact. A recent outbreak in Kiel, proved to 
be paratyphoid, is assumed by Fischer to have been 
caused by infected meat, on account of the peculiar 
distribution of the cases among the patrons of a 
particular market. Kurth also attributed a small 
epidemic to either uncooked meat or milk. Fischer 
mentions 50 cases in East Holstein which probably 
were infected by the milk of two cows. Shortly 
after the epidemic began the cows died and para- 
typhoid bacilli were cultivated from the muscles, 



286 INFECTION AXD IMMUNITY. 

spleen, liver and intestines. De Feyf er cites an in- 
stance in which the disease apparently was trans- 
mitted through the water of a stream in which the 
clothing of the first patients had been washed. In 
another instance, a regimental infection was traced 
to the discharges of a single soldier, the water sup- 
ply having become contaminated through a defec- 
tive water closet. 
characteristics Paratyphoid, like tvphoid fever, is accompanied 

of the Disease. , j -. ■, " -, , A -. 

by an enlarged spleen and many rose spots. Al- 
though severe symptoms may be present for a time, 
the course of the disease usually is mild and the 
mortality is low. The incubation period approxi- 
mates that of typhoid. In the few cases which 
have come to autopsy the intestinal lesions have 
varied from a mild ileocolitis with an intact mu- 
cous surface to a condition of superficial ulcera- 
tion. The involvement of Peyer's patches and the 
solitary follicles which is so characteristic of ty- 
phoid is absent, although these structures may be 
moderately swollen. The mesenteric lymph glands 
are not markedly involved and there is little pro- 
liferation of the lymphoid or endothelial cells 
(Wells and Scott). The disease has no specific 
anatomic lesion. 
^stance 'a^d The organisms are found in the blood and vari- 
Distribution. ous organs, in the rose spots, urine and feces of the 
patients. Practically nothing is known- of the oc- 
currence of the bacilli outside the body. Because 
of their presence in the stools and urine of the pa- 
tients, the methods of dissemination and infection 
doubtless are similar to those concerned in typhoid. 
The bacillus is said to have a marked resistance to 
-heat, withstanding 60° C. for 30 minutes and 
not all cells being killed during one hour at 



PARATYPHOID. 287 

this temperature. This may explain the fact that 
the virus is not always killed by cooking the meat. 
The organism probably has a wide distribution 
because of the occurrence of the infection in vari- 
ous parts of the world. 

The toxicity of the bacilli depends on the exist- 
ence of a fixed endotoxin; a soluble toxin is not 
produced. 

The principles of prophylaxis against typhoid 
also apply to paratyphoid fever, with the addition 
that in the latter disease the possibility of meat in- 
fection must be kept in mind. 

The serums of patients and immunized animals 
acquire bactericidal and agglutinating powers for 
the organism. 

There is no serum therapy for the infection, nor 
has the occasion arisen to attempt vaccination. 

Serum from a paratyphoid patient may aggluti- Agglutination 
nate the homologous bacillus in a dilution of cultures. 
1/1000 or 1/2000 or more (E. H. Kuediger), 
whereas the typhoid bacillus is agglutinated only 
in low dilutions by the same serum. How- 
ever, bacillus A and bacillus B are not identical 
in their agglutinable properties; in this respect 
it is stated that the latter is more closely re- 
lated to the typhoid bacillus than the former. 
The agglutination test is said to have a higher 
diagnostic value than the Gruber-Widal reaction 
in typhoid, a stronger agglutinating power being 
developed in the serum of the patient. Never- 
theless, the formation of coagglutinins may render 
the test confusing if proper serum dilution is not 
practiced. Conclusions should not be attempted 
until the test has been performed with both strains 
of the paratyphoid bacillus and with the typhoid 



288 INFECTION AND IMMUNITY. 

bacillus. As in typhoid, early diagnosis may be 
best accomplished by bacteriologic examination of 
the blood. 

III. ACUTE EPIDEMIC DYSENTERY. 

In addition to amoebic dysentery, we have be- 
come familiar with an acute dysenteric infection 
which appears epidemically in both tropical and 
temperate climates, and prevails especially in the 
summer months. Such epidemics occur extensively 
in Japan, where the mortality may be 24 per cent. ; 
in the Philippines, United States, Germany and 
other European countries. In industrial settle- 
ments in Germany the mortality is about 10 per 
cent. (Kruse). The incubation period may be as 
short as two or three days. In mild cases the pa- 
tient may recover in from four to eight days, 
whereas severe cases last from two to four weeks, 
and may terminate fatally. Occasionally the in- 
fection lasts sufficiently long to be considered 
chronic. 
Two Types In 1898, Shiga, basing his conclusions on posi- 
of Bacilli. ^ ye resu ^ s w ith the agglutination test and on the 
constant presence of the organism in the stools of 
the infected, identified as the cause of the disease, 
in Japan, a microbe which is known as Bacillus 
dy sentence, (Shiga). Flexner, in 1900, made simi- 
lar observations on epidemic dysentery in Manila, 
and his organisms, or one of them, differing slight- 
ly from that of Shiga, is called Bacillus dijsenterim 
(Flexner), or the Flexner-Harris bacillus, Harris 
being the name of a patient from whom this 
typical strain was cultivated. Kruse (1901) found 
both the Shiga and Flexner types in Germany, 
needlessly giving the name of "pseudodysentery" 
bacilli to the latter. In this country similar organ- 



ACUTE DYSENTERY. 289 

isms have been found as the cause of institutional summer 
dysentery by Vedder and Duval, of summer diar- Diarrheas - 
rheas of infants by Duval and Bassett, and by Wol- 
stein. It is the belief of Vedder and Duval that 
acute dysentery, the world over, "whether sporadic, 
institutional or epidemic, is caused by the dysen- 
tery bacillus/' We must note, however, that the 
organism is not found in all cases of clinical dys- 
entery, even by skilled bacteriologists. "Clinically, 
24 of our 97 cases in which the dysentery bacilli 
were found did not differ from the cases of ileocoli- 
tis in which the dysentery bacilli were not found." 
(Weaver and others.) It seems certain, neverthe- 
less, that Bacillus dysenteries is the most impor- 
tant cause of acute dysentery. It rarely occurs in 
the stools of healthy individuals. 

The organisms of Shiga and Flexner differ in 
their actions on sugars (i. e., in their acid-forming 
powers) and in their agglutinability ; the "Flex- 
ner" type is the stronger acid-former. An artificial- 
ly produced immune serum which is specific for one 
organism has rather higher agglutinating and bac- 
tericidal powers for the corresponding type, but 
low for the other. In this country the "Flexner" 
bacillus is much more common than that of 
"Shiga," but here and abroad both types are met, 
and sometimes in the same individual. Several 
other organisms have been cultivated from dysen- 
teric patients, but the variations from these two 
types are slight. All are certainly very closely re- 
lated. 

The organism is somewhat thicker than the ty- characteristics 
phoid bacillus, but probably is non-motile, al- 
though Vedder and Duval, in opposition to others 
(Lentz), claim to have demonstrated flagella. It 



290 INFECTION AXD IMMUNITY. 

often shows a polymorphous appearance in cul- 
tures, but forms no spores. It is Gram-negative. 
It lives for from 12 to 17 days when dried 
(Pfuhl) ; direct sunlight kills it in 30 minutes, 
1 per cent, carbolic acid in 30 minutes, 5 per cent, 
carbolic acid plus corrosive sublimate (1/2000) 
almost instantaneously. It is thought that it may 
live over winter and cause fresh outbreaks in the 
spring (Kruse). 
Distribution The bacillus is found only in the stools of the 
infected, in the mucous or muco-hemorrhagic por- 
tions of which it exists almost in pure culture, few 
colon bacilli being in the immediate vicinity; it 
has not been found in the blood or urine. In fatal 
cases, Shiga found it only in the intestinal ulcers 
and swollen lymphoid structures and in the mesen- 
teric lymph glands. Flexner mentions its occur- 
rence in the liver. The organism, if it reaches the 
circulation at all, either does so in small quantities, 
or is rapidly destroyed by the blood. The infection 
resembles cholera, but differs from typhoid and 
paratyphoid in this respect. An observation by 
Markwald (cited by Lentz) indicates, however, 
that the bacilli may reach the circulation. A 
woman sick with dysentery gave birth to a child, 
which died within a few hours. Dysenteric changes 
were found in the intestines, and the bacillus of 
dysentery was cultivated from the diphtheritic de- 
posits on the intestines, from the meconium and 
from the heart's blood. The organisms must have 
reached the child through the placenta from the 
circulation of the mother. 
Lesions. The intestinal lesions vary from a simple in- 
flammatory hyperemia to rather extensive superfi- 
cial necrosis (diphtheritic inflammation), which 



ACUTE DYSENTERY. 291 

rarely extends below the submucosa. Such foci 
are said to be the most marked in the descending 
colon and sigmoid where mechanical injury is 
more likely to occur. The necrotic areas separate 
by sloughing, leaving superficial ulcers. The lym- 
phoid follicles are swollen and infiltrated with 
polymorphonuclear leucocytes, which also accumu- 
late in the dilated lymph spaces of the intestinal 
wall. The ileum is so commonly involved that the 
condition is called an ileocolitis. Conspicuous 
changes are not found in the mesenteric glands or 
spleen. The liver and kidneys commonly show 
parenchymatous degenerations. 

The dysentery bacillus is highly toxic. Subcu- Toxicity of 
taneous injections of killed cultures produce in 
man a more profound reaction than the organism ' 
of either cholera or typhoid. Ordinary laboratory 
animals are so susceptible that they are immunized 
with difficulty; the horse is less susceptible. The 
toxicity of the organism apparently depends on an 
intracellular toxin (an endotoxin) rather than on 
a soluble toxin. When living or killed cultures 
are submitted to autodigestion in salt solution 
(Conradi, Nisser and Shiga), or when bouillon 
cultures are allowed to grow for 30 days, the 
liquids are found to be toxic after the organisms 
are removed. In both instances this toxicity prob- 
ably depends on the liberation of endotoxins. The 
question as to whether the bacillus in the intes- 
tines produces a soluble toxin which is absorbed by 
the lymphatics, is undetermined. It seems more 
probable that the conditions are analogous to those 
of cholera, intoxication resulting from the libera- 
tion of endotoxins by the solvent action of the tis- 
sue fluids or cells on the bacilli. Dysenteric symp- 



292 INFECTION AND IMMUNITY. 

toms are not produced in animals by feeding the 
organisms. 
Dissemination The stools of the patient are the only known 
and infection. g01i:rce f ^ e organism and it continues to be ex- 
creted during convalescence. Latent or chronic 
cases are a source of danger to a community. Al- 
though the conditions outside the body are not 
favorable for the growth of the organism, it may 
remain living and virulent for several months. The 
methods of infection appear identical with those 
seen in typhoid. Water infection seems certain, 
and indirect transmission is acomplished by con- 
tact with the discharges. The best examples of 
contact infection are found in institutional epi- 
demics. 
Prophylaxis The first essential for prophylaxis is correct di- 
an tibmtyi agnosis, for which the agglutination test and bac- 
teriologic examination of the stools are essential. 
Disinfection and other precautions should be prac- 
ticed as rigidly as in typhoid. The patient should 
not be discharged until the stools are free from 
dysentery bacilli. 

Poorly nourished individuals are particularly 
susceptible to infection, and among them the mor- 
tality is high. The disease is most common among 
young children, old people, and those who are con- 
fined in institutions. The conditions in Japan, 
however, where from June to December of one year 
nearly 90,000 were attacked, and in Germany, 
where severe epidemics occur in industrial com- 
munities, indicate that susceptibility is quite gen- 
eral. Digestive disturbances and enteritis from 
other causes are said to be predisposing factors. 
The normal serums of man and animals have very 
little bactericidal power for dysentery bacilli. 



ACUTE DYSENTERY. 293 

The subject of acquired immunity to dysentery immunity. 
is hardly on a satisfactory basis. The serum of 
convalescents shows a distinct bactericidal power 
for the organism, and there is good reason to be- 
lieve .that the acquired immunity persists for some 
time after the disappearance of the bactericidal am- 
boceptors, an event which takes place rather early. 
As in typhoid, animals which through immuniza- 
tion have once been stimulated to produce anti- 
bodies, form them much more readily on the occa- 
sion of a subsequent inoculation. This acquired 
facility in producing antibodies may be a factor in 
acquired immunity. By immunizing horses, 
serums of rather high protective power have been 
obtained. Kruse prepared a serum of which 
1/80000 gram would save a guinea-pig from a dose 
of the bacilli which killed a control in 20 hours. 
It is assumed that the protective power of this 
serum is due to its bactericidal action. The anti- 
toxic serum which Eosenthal prepared, by immun- 
izing with 30 days' old bouillon cultures, protected 
not only against the toxin, but also against the 
bacilli ; and conversely an antibacterial serum pro- 
tected against the toxin (cited by Lentz). Such 
results leave us very much in doubt as to the exist- 
ence of a true antitoxic serum. 

The value of protective inoculations is not well vaccination 
established. Shiga at one time practiced mixed Therapy!" 1 
active and passive immunization (bacilli plus im- 
mune serum) on 10,000 individuals. This did not 
decrease the number of infections, although a lower 
mortality resulted. Shiga claims that the thera- 
peutic use of his serum reduces the mortality to one- 
third that of the untreated. The serum of Kruse, 
and also that of Rosenthal, are said to be cura- 



294 INFECTION AND IMMUNITY. 

tive; the discharges rapidly decrease in number 
and the course of the disease is shortened. In the 
hands of the Eockefeller Institute, antidysentery 
serum proved of no distinct value. 
Agglutination. The agglutination reaction with the serum of 
patients shows great variability. It is sometimes 
absent in spite of the presence of bacilli in the 
stools, and often disappears rapidly during con- 
valescence (in two weeks occasionally). It is rarely 
as high as in typhoid. In infantile diarrheas ag- 
glutinins appear at about the end of the first week 
of illness (Duval and Bassett). Evidently mild 
cases in which the course of the disease is from 
four to eight days may not be recognized by means 
of the agglutination reaction before the period of 
convalescence. In chronic cases the agglutinating 
power may persist for three or four months. No 
reaction was obtained with the typhoid bacillus. 
Rruse considers the reaction diagnostic when it 
occurs in a dilution of 1/50 ; Pfuhl, 1/30. Strong 
co-agglutinins for other organisms, i. e., above 
1/50, have not been observed (Lentz). The tests 
should always be performed with both the "Shiga" 
and "Mexner" types, as the two have not identical 
agglutinable properties, and either organism may 
be the cause in a given instance. The absence of 
the reaction does not exclude a dysenteric infec- 
tion positively. Bacteriologic examination of the 
stools is important, often necessar} r , for early diag- 
nosis. 

IV. MEAT POISONING BY BACILLUS ENTERITIDIS. 

Botulism as a special form of meat poison- 
ing and the occasional production of paratyphoid 
by infected meats, have been mentioned. In 
addition to these, more or less extensive epidemics,. 



BACILLUS ENTERITIDIS. 



295 



Bacillus 
Enteritidis. 



supposed to be due to ptomains which were found 
in putrid meat, have occurred not infrequently. 
It is now well established that most epidemics of 
this character are caused by pathogenic bacteria 
which are present in the meat, whereas putrid de- 
composition of the latter is an unessential incident. 

Gartner, in 1888, had the opportunity of study- 
ing an epidemic caused by the meat of a cow which 
had been slaughtered in extremity. The symptoms 
differed from those of botulism or jmratyphoid, as 
described below. He obtained from the muscle and 
spleen of the cow, and from the spleen of a man 
who had been fatally poisoned, an organism which 
has since been known as Bacillus enteritidis (Gart- 
ner). The same bacillus, or organisms which re- 
semble it closely, have been obtained repeatedly 
during similar epidemics, both from the suspected 
meat and from the organs in fatal cases (intes- 
tines, blood, spleen, etc.). Drigalski, from a com- 
parative study of several strains which had been 
obtained from different sources, concluded that 
all are members of a closely related group of or- 
ganisms, the group of Bacillus enteritidis. His 
conclusions were based on cultural properties and 
agglutination tests. 

The typical organism is a short rod, often ovoid 
in shape, possesses from four to twelve long flag- 
ella and has moderate motility. It ferments vari- 
ous sugars and is not stained by Gram's method. 
Variations among individual strains need not be 
discussed here. 

According to v. Ermengem, and also Drigalski, Pathogenicity. 
its pathogenicity depends on the elaboration of a 
soluble but heat-resistant toxin. Bouillon cul- 
tures twelve days old, in which the bacteria have 



296 INFECTION AND IMMUNITY. 

been killed by heat, also similar cultures from 
which the bacteria have been removed by nitration, 
are toxic for mice and guinea-pigs (Drigalski). It 
is noteworthy, however, that relatively large quan- 
tities of the bouillon were necessary to kill guinea- 
pigs (4.0 c.c.) which is in contrast to the toxins of 
diphtheria and tetanus. The rapidity with which 
symptoms develop following the ingestion of in- 
fected meat is a further indication of the exist- 
ence of this soluble toxin, which, it would seem, is 
formed in considerable quantities in the meat. 
Symptoms occasionally develop so quickly as 
to suggest some strong metallic poisoning. With- 
in a few hours vomiting, violent diarrhea and 
colicky pains set in, followed by more or less 
collapse, weakness, headache and not uncom- 
monly by erythematous, urticarial or herpetic 
eruptions. Fever is absent or inconspicuous. 
The mortality is not high, from 2 to 5 per cent. ; 
convalescence is said to be slow. Nephritis and 
catarrhal pneumonia have been noted as sequelae. 
Autopsy shows the anatomic changes of an acute 
gastroenteritis, sometimes of hemorrhagic charac- 
ter, with swollen Peyer's patches; the large intes- 
tine is not greatly involved. The spleen may be 
swollen and the kidneys degenerated. The ana- 
tomic findings are not specific. 
Sources of It has been shown in numerous instances that 
the cattle or horses (Drigalski) which furnished 
the meat were sick with an intestinal or general 
infection with Bacillus enteritidis before they were 
slaughtered. "In a very large number of cases it 
can be demonstrated that the animals from which 
the meat was taken had been slaughtered in ex- 
tremity or had died recently, and, indeed, that 



Infection. 



BACILLUS ENTERITIDIS. 297 

they had (in certain instances) died before they 
could be slaughtered. Most often they suffer from 
septic inflammatory processes or from traumatic, 
puerperal or other sorts of septicemia, or from 
other ill-defined pathologic conditions which are 
accompanied by symptoms of enteritis or intestinal 
or pulmonary inflammations." (v. Ermengem.) 
Subsequent infection of the meat by Bacillus en- 
teriti&is, i. e., after slaughtering, has not been 
noted. 

The organism occurs in the blood and various Growth in 
organs of infected animals and man. Poisoning e M ' 
most commonly arises when the meat has been 
kept for several days, which usually is the case by 
the time it is made into some form of sausage. In 
the meantime the bacilli have proliferated and ad- 
ditional toxin has been produced. In at least one 
instance a certain number of patients who ate the 
meat while it was fresh suffered moderate or no 
intoxication, whereas those who ate it several days 
later became violently ill. In an epidemic caused 
by horse meat Drigalski found that "only those 
persons suffered from intoxication who ate the 
meat after it had lain for eight days or more." 

The micro-organism is very resistant to heat Toxin in 
and the temperature which is attained in ordinary 
cooking may not be sufficient to kill the bacteria 
which are remote from the surface. Even in the 
event that the meat has been thoroughly sterilized, 
the heat-resistant toxin may be present in suffi- 
cient quantity to cause the intoxication. Not 
much is known concerning the distribution of 
Bacillus enteritidis. v. Ermengem suspects that 
it may be a factor in poisoning by oysters and fish, 
but this remains undetermined. 



298 INFECTION AND IMMUNITY. 

Agglutinins. The blood acquires specific agglutinins during 
the course of infection. Even eight days after the 
beginning of symptoms agglutination may be ob- 
tained in dilutions varying from 1/200 to 1/4000. 
The agglutinins disappear very rapidly. Working 
with artificially prepared immune serum, Drigal- 
ski determined the existence of coaggiutinins for 
typhoid and paratyphoid bacilli. 

We should bear in mind the likelihood that 
meats poisoned with Bacillus enteritidis, as well as 
by paratyphoid bacilli, may be encountered in 
America, as well as in foreign countries. 

V. BACILLUS COLI COMMUNIS. 

Bacillus coli communis, Bacterium coli com- 
mune, or the colon bacillus, is the type of a large 
group of organisms the members of which show 
individual differences, but possess certain domi- 
nant features in common. The typical colon bacil- 
lus ferments various sugars, with the production of 
gas, is a strong acid producer and curdles milk. It 
is flagellated, has moderate motility and does not 
stain with Gram's method. One type or another 
is the normal inhabitant of the intestinal tract of 
many animals, and, although the organisms are 
widely disseminated in nature, their occurrence is 
related directly or indirectly to the distribution of 
feces. 
Resistance. Its optimum temperature for growth is 37° C, 
and above 46° C. it does not proliferate. It is 
killed at a temperature of from 60° to 61° C. in 
from five to fifteen minutes; it is not killed by 
such low temperatures as from — 20° to — 24° C. 
It resists absolute desiccation for periods varying 
from a few days to several months (different ob- 
servers). Direct sunlight kills 99 per cent, of the 



COLOX BACILLUS. 299 

germs in two hours (Billings and Peckharn), and 
the}' are very susceptible to ordinary antiseptics. 
The normal serums of mam^ animals are bacterici- 
dal for the colon bacillus. 

Escherich, a noted authority on this organism, 
lays down the principle that that strain which may 
be cultivated from the feces of the nursing child 
should be considered as the typical Bacterium coll 
commune, maintaining that a constant type of or- 
ganism is found under these conditions. It is said 
to occur here in relatively pure culture. 

Within a very short time after birth the organ- Distribution in 
ism is found in the intestines of infants, and its the,ntestines - 
method of entrance has been the subject of much 
discussion. In view of its ready dissemination it is 
not difficult to conceive of many circumstances 
which favor its entrance. Having once reached 
the intestines, it finds there its optimum conditions 
for growth. The small intestines in man are 
rather free from colon bacilli and other organisms 
as well. This, perhaps, is due, to some extent, to 
the alkalinity of the medium and to the rather 
rapid flow of the intestinal contents at this point. 
The colon bacillus reaches its maximum develop- 
ment in the large intestine, where, in fact, the 
whole bacterial flora of the intestines is most con- 
centrated. 

In view of the fact that the colon bacillus is a Normal 
normal inhabitant of the intestines, the conception 
has occurred to many that it may be of distinct 
value to the economy, either because of the action 
it has on certain foods (splitting of carbohy- 
drates), or because in some obscure way it in- 
fluences favorably the assimilation of foods, or in 
that it antagonizes other bacteria of distinct patho- 



300 INFECTION AND IMMUNITY. 

genie powers which also exist normally in the in- 
testines or reach them through accident. This is 
not the place to consider these questions in detail, 
and they are on none too definite a basis. It may 
be stated, however, that the colon bacillus and an- 
other closely related organism, Bacillus lactis aero- 
genes, distinctly antagonize the action of certain 
proteolytic bacteria which appear to be associated 
with the putrid decomposition of milk and other 
proteid-containing foods. Bacteria of the latter 
type exist in the intestines. Uhsterilized milk has 
a natural resistance to putrid decomposition, and 
sterilized milk which contains the colon bacillus or 
Bacillus lactis aerogenes has a similar resistance. 
These two bacteria flourish in the presence of car- 
bohydrates, which they decompose with the liberal 
formation of acids, and through these acids they 
"limit intestinal putrefaction and influence (fa- 
vorably) pathologic processes which are caused or 
maintained by the existing 'alkaline fermenta- 
tion' " (Escherich and Pfaundler). That the or- 
ganisms in question antagonize the action of putre- 
factive bacteria has been shown in test-tube experi- 
ments (Hirschler). 
Pathogenicity. * Since the time that Emmerich upheld the colon 
bacillus (or a colon-like microbe) as the cause of 
Asiatic cholera (1885), opinion as to the patho- 
genic powers of the organism has undergone 
many fluctuations. Following Koch's demonstra- 
tion of the vibrio of cholera as the etiologic factor 
in cholera, the colon bacillus was, so to say, re- 
pressed as a pathologic agent. Later, and especially 
in France, great significance was again attached to 
it. The condition still shows a great deal of chaos, 
although, on account of more refined technic and 
the elimination of other organisms, as the dysen- 



COLON BACILLUS. 301 

tery and paratyphoid bacilli and Bacillus enteriti- 
dis, from the colon group proper, we are, perhaps, 
on the way to a more satisfactory understanding 
of the pathogenicity of this organism. Although 
certain authors hold at the present time that the 
colon bacilli which normally inhabit the intes- 
tines are devoid of virulence, such a radical posi- 
tion is open to question. Avirulent strains have 
often been encountered, however. 

As harmless as the colon bacillus appears to be virulence 
when confined in the intact intestines, its viru- 
lence for animals, although low, has been demon- 
strated in many instances. A bouillon culture of 
the average bacillus which has grown for from one 
to two days, and when freshly cultivated from the 
stools, causes the death of a 300 to 400 gram 
guinea-pig in two or three days, when given intra- 
peritoneally in a dose of from 2 to 3 c.c. Subcu- 
taneous inoculations, the feeding of cultures, their 
introduction into the bladder and biliary passages 
induce inflammatory processes. It is stated 
(Escherich) that whether the cultures are intro- 
duced into the skin, peritoneum or vessels, symp- 
toms of severe gastroenteritis are produced, not 
unlike Asiatic cholera. This fact doubtless in- 
fluenced Emmerich in considering the organism as 
the cause of cholera. The general symptoms are 
those of an acute febrile intoxication. 

The organism is most pathogenic when freshly 
cultivated, and soon loses its virulence after re- 
peated transplantations. As in the case of some 
other bacteria, virulence may be re-established by 
"passage" through suitable animals. 

The cultivation of the colon bacillus from the 
blood and organs of man at autopsy has not the 



302 INFECTION AND IMMUNITY. 

virulence significance which was once attached to it. It has 
been recognized that the colon bacillus in particu- 
lar, and less commonly other intestinal organisms, 
may enter the circulation a short time before death, 
at a time when resistance is very low, and may 
obtain the general distribution which is so often 
encountered at autopsy; this is the so-called "ago- 
nal invasion," which may occur without much re- 
gard to the primary cause of death. The condi- 
tions which favor agonal invasion remain, to a 
large extent, obscure. Distinct defects of the in- 
testinal mucosa probably are not essential, al- 
though this view has its representatives. In states 
of low vitality in which resistance to infection is 
decreased (disappearance of complement!), the or- 
ganisms find conditions favorable to proliferation 
when they have once reached the circulation. In 
spite of the low virulence of the colon bacillus, it 
commonly has a certain amount of toxicity and it 
may often be of significance even as an agonal in- 
fection. 

Postmortem invasion of adjacent structures, as 
the gall bladder and liver through the biliary pas- 
sages, and of the peritoneum through the intesti- 
nal wall, also occurs. 
True It has been shown that the colon bacillus occa- 
sionally causes the following conditions : Suppura- 
tive cholecystitis which may extend to the liver, 
peritonitis, septicemia, meningitis, cystitis, pyeli- 
tis and ascending suppurative nephritis, and ab- 
scesses in various organs, including suppurative 
processes in the middle ear. In one or more in- 
stances it has been thought that it caused vegeta- 
tive endocarditis. Probably colon infections of the 
gall bladder do not occur in the absence of biliary 



Infections, 



COLOX BACILLUS. 303 

stasis. Ordinarily cases of peritonitis in which 
the colon bacillus is encountered also show the 
presence of other pathogenic organisms, as strepto- 
cocci or staphylococci; this is always the case in 
perforation peritonitis. Doubtless wrong conclu- 
sions have been drawn in many instances as to the 
bacteriology of peritonitis from the fact that the 
colon bacillus readily overgrows many other bac- 
teria in culture media. 

Escherich attributes great importance to this or- cystitis. 
ganism as the cause of cystitis, especially in chil- 
dren, and states that it is probably the most com- 
mon cause of cystitis, pyelitis and ascending sup- 
purative nephritis. In 58 of 60 cases of cystitis in 
children the colon bacillus was found either alone 
or in mixed cultures. An increased agglutinating 
power of the patient's serum for the organism cul- 
tivated from the urine is noted in these cases. 

Great interest attaches to the colon bacillus in Diarrheas. 
relation to enterocolitis and dysenteric diseases. 
Escherich speaks of an enteritis follicularis, or 
colitis contagiosa, or colicolitis, epidemics of which 
have been noted at different times. A number of 
these epidemics occurred before the identification 
of the dysentery bacillus, and certain of them may 
have been true dysenteric infections. Neverthe- 
less, dysentery bacilli are not found in all cases of 
enterocolitis, and the probability that genuine 
cases of colon enteritis occur can not as yet be neg- 
lected. 

A specific colon toxin has not been obtained. 

Immunization with the colon bacillus causes the 
formation of bactericidal amboceptors and agglu- 
tinins. 

Not all strains of the colon bacillus are identical 



304 INFECTION AND IMMUNITY. 

Agglutination, in their agglutinogen^ receptors. A serum which 
agglutinates one colon strain does not necessarily 
agglutinate all strains. The reaction, according to 
Paltauf and others, is largely an individual one. 
The serum of a patient with a colon infection will 
agglutinate the strain causing the disease, but may 
not affect other strains. Hence, for diagnostic 
purposes, the test must be performed with the cul- 
ture which has been obtained from the patient. 
Pfaundler says in reference to colicolitis that if 
other colon infections can be excluded, and if the 
serum of the patient gives the agglutination reac- 
tion in a dilution of 1 to 50 with the bacillus 
which has been cultivated from the stools, colon 
infection is indicated (Paltauf). 

VI. CHOLERA. 

In 1883 Koch discovered the Vibrio cholera and 
cultivated it from the stools of cholera patients. 
The organism may be cultivated from the stools of 
the patients invariably, and is never found in other 
diseases nor in normal stools, except in the case of 
non-susceptible persons who may be encountered 
during an epidemic. The latter are a source of 
danger as "cholera carriers." 
Characteristics Typically the cholera vibrio is about 1.5 microns 
long and one-fourth as broad. The cells of young 
cultures have the so-called comma shape which has 
given the organism the name of the comma bacil- 
lus. The form in reality is that of a segment of a 
spiral. When two cells are attached end to end an 
S-shape may be produced, and long spirals are 
made up of many cells which are joined at the 
ends. In old cultures the cells may assume the 
form of thick rods or even appear coccus-like. The 
vibrio possesses a single long flagelluin, which is sit- 



ofthe Orqan- 



CHOLERA. 305 

uated at the end. Although two, four and six flag- 
ella have been described, Kolle states that such or- 
ganisms are vibrios of another nature.. In the 
character and rapidity of their movement, as seen 
in a hanging-drop, Koch compares them to a 
swarm of mosquitoes. Old cultures may lose their 
motility to a large extent. The cholera vibrio 
does not form spores, although certain involution 
forms simulate them. It stains readily with the 
ordinary anilin dyes and is Gram negative. 

The comma . bacillus grows readily in alkaline cultivation 
culture media with characteristic appearances; it stools. 
is an obligate aerobe under artificial conditions, in 
spite of the fact that it flourishes in the intes- 
tines. The optimum temperature lies between 30° 
and 40° C. A very simple method of obtaining the 
organism in pure culture from the stools was dis- 
covered by Koch. In tubes of peptone bouillon 
which have been inoculated with the feces of a 
patient, the vibrio proliferates rapidly and within 
a few hours exists in almost pure culture at the 
surface of the liquid. Isolated colonies are ob- 
tained by transferring a small amount of the sur- 
face fluid to tubes of liquefied gelatin, then plating 
the latter. The colonies appear in a few hours as 
small translucent points from which pure cultures 
are made on a suitable medium. For more positive 
identification agglutination tests are performed 
with anticholera serum. The Eoyal Institute for 
Infectious Diseases (Berlin) keeps on hand a dried 
serum of known strength (1-10,000) for this pur- 
pose. The tests being made with high dilutions, 
coagglutinins for other vibrios are practically elim- 
inated. To the agglutination test may be added 
the "Pfeiffer experiment," in which the protective 



Identification. 



306 INFECTION AND IMMUNITY. 

power of an anticholera serum is determined when 
guinea-pigs are infected intraperitoneal!}- with the 
suspected culture. If the serum shows a protective 
power against this organism which approximates 
that shown against a known cholera vibrio, or, if 
the organisms are dissolved, the diagnosis of chol- 
era is justified. In performing such experiments 
the serum is mixed with the culture before injec- 
tion. 
Resistance. The resistance of the cholera vibrio is very low. 
It dies in about two hours when dried (Koch) and 
on this account dust infection is thought not to 
occur. It is killed instantly by the boiling tem- 
perature, and in five minutes at 80° C. It is ex- 
tremely susceptible to carbolic acid (killed by 1 
per cent, in five minutes), corrosive sublimate (1 
to 2,000,000 or 3,000,000 in from five to ten min- 
utes), and to acids. Calcium chlorid is an effi- 
cient disinfectant when thoroughly mixed with the 
stools. The micro-organism lives in distilled water 
not longer than twenty-four hours, in ordinary 
water for several days to several weeks, and in one 
instance it was cultivated from the water of an 
aquarium after several months. Its life is short in 
the presence of putrefactive bacteria and rapidly- 
growing saprophytes, dying in sewer water in from 
twenty-four to thirty hours (Koch). Because of 
the large overgrowth of other organisms, the vibrio 
can rarely be cultivated from the stools later than 
from one to three days after death. Its life in and 
on foods depends on the reaction (alkalinity is 
favorable), and on the presence or absence of 
moisture. It lives longer in sterilized milk (ten 
days) than in that which contains other micro-or- 
ganisms. 



CHOLERA. 



301 



Infection develops in the small intestines fol- 
lowing ingestion of the organisms. Infection by 
way of the lungs or through wounds does not take 
place. In the patient the living vibrio occurs only 
in the intestines, and it is excreted only with the 
feces. So far as known, it has no normal habitat 
outside the body, although a stream or other water 
supply may contain the vibrio over a long period 
through constant reinfection of the water. This 
can only occur, directly or indirectly, through the 
stools of patients. The washing of soiled linen or 
bathing in water which is used for drinking and 
other household purposes have caused outbreaks of 
cholera. The water supply of a city may be in- 
fected by the discharges of patients who are con- 
fined to a ship. Convalescents may retain virulent 
organisms in their stools for forty-eight days 
(Kolle), and, as stated, healthy persons who are 
insusceptible to cholera and who have resided in 
an infected district may carry virulent vibrios in 
their intestines. These conditions have contrib- 
uted to the futility which, to a large degree, has 
met attempts to limit the extension of cholera by 
quarantine measures. Cholera extends from coun- 
try to country along the lines of travel. In some 
instances it has been possible to trace the origin 
of widespread epidemics to the delta of the Ganges, 
a region in which the disease is endemic. Pilgrims 
from India carry the infection to Mecca, and pil- 
grims from Egypt carry it to their native land on 
their return from Mecca. Either from Egypt, or 
through Arabia, Asia Minor and Southern Russia 
or Turkey, cholera has, with more or less rapidity, 
extended to Western Europe. The development of 
rapid transit has increased the rapidity with which 



Infection 
Atrium and 
Dissemination. 



Epidemics. 



308 INFECTION AND IMMUNITY. 

cholera may extend. From Europe the disease has 
been carried to various ports of the western conti- 
nent, Canada, the West Indies and southern ports 
of the United States, from which extension has oc- 
curred to different sections. Of six widespread 
epidemics of the past one hundred years, three 
have involved the United States, reaching consid- 
erable proportions. The means of introduction is 
not always apparent. 

As in typhoid, two types of epidemics are known, 
the two often being associated : First, that caused 
by water infection, and, second, that in which the 
disease spreads by direct and indirect contact. The 
explosive character of an epidemic caused by in- 
fection of a water supply is much more striking 
than in the case of typhoid fever. In large cities 
hundreds, or thousands, may be striken within a 
day. The brief incubation period, from twelve to 
twenty-four hours, contributes to the acuteness of 
the outbreak. The distribution of a "water- 
borne" epidemic corresponds with the distribution 
of the infected water. A remarkable occurrence il- 
lustrating this point was noted in the epidemic 
which attacked Hamburg in 1892. In certain 
streets in which the residents of the two sides ob- 
tained their water supply from different sources, 
one of which was infected, cholera was limited to 
that side which was supplied with infected water. 
Only irregular cases due to contact infection oc- 
curred on the opposite side of the street. 

Epidemics which are due solely to contact infec- 
tion develop slowly and irregularly. A common 
incident is the successive involvement of the mem- 
bers of a family, whereas others in the immediate 
neighborhood are unaffected. Water-borne epi- 



CHOLERA. 



309 



of Animals. 



demies are invariably complicated by the occur- 
rence of contact infection. The methods of con- 
tact infection are not different from those men- 
tioned under typhoid fever. Food or milk which 
has been infected by contaminated water or by 
other means may cause the development of isolated 
groups or cases. 

Animals do not contract cholera under natural Susceptibility 
conditions. By rendering the gastric contents of 
guinea-pigs alkaline and introducing cultures into 
the stomach through a tube, Koch induced a chol- 
era-like process from which the animals died with- 
in from twenty-four to thirty-six hours; an intra- 
peritoneal injection of opium, to quiet peristalsis, 
seemed to be necessary for the success of the ex- 
periment. Similar results were obtained in very 
young rabbits by feeding cultures to them (Issaeff 
and Kolle, iMetchnikoff). Guinea-pigs withstand 
the subcutaneous inoculation of moderate amounts, 
but are very susceptible to intraperitoneal inocula- 
tion. Intravenous injections are exceedingly toxic 
for rabbits, and a fatal cholera-like condition with 
localization of the organisms in the intestines and 
intestinal mucosa has been produced in this way 
(Thomas). 

The essential poison of the cholera vibrio is in- 
tracellular, and becomes free only after solution of 
the bacterial cells. Cultures which are killed care- 
fully as by chloroform vapor (Pfeiffer) are highly 
toxic, although the fluid alone is non-toxic. The 
nitrates of young cultures have little or no poison- 
ous action. The toxicity of older nitrates is due 
partly to the solution of the bacteria with conse- 
quent liberation of endotoxin, and perhaps also to 
secondary disintegration products which have a 



Endotoxin. 



the Intestines. 



310 INFECTION AND IMMUNITY. 

certain toxicity. The soluble toxin of Metchni- 
koff, Koux, and Taurelli-Salimbeni is a dissolved 
endotoxin and not a secretion of the living cells, 
according to Kolle. 
Conditions in Koch considers that cholera is an acute infec- 
tions process of the intestinal epithelium, whereas 
the general condition is one of acute intoxication. 
It is assumed that the condition in the intestines 
corresponds to that in the culture media, i. e., that 
here, too, no true soluble toxin, comparable with 
that of diphtheria or tetanus, is secreted, but that 
the toxin which eventually reaches the circulation 
is that which is liberated from the bacteria after 
the latter have been dissolved by the bacteriolysin 
of the plasma, or perhaps by the leucocytes. Doubt- 
less a great deal of endotoxin is liberated in the in- 
testinal canal, but it is Koch's conception (cited 
by Kolle) that the primary intoxication comes 
from those organisms which have penetrated be- 
tween and beneath the epithelial cells and here 
have undergone solution. One effect of the toxin 
in this situation is to cause desquamation of the 
intestinal epithelium, as a consequence of which 
rapid absorption of the toxin from the intestinal 
canal takes place through the denuded surface. 
This theory supposes that the toxin is not readily 
absorbed through the intact epithelium. The liv- 
ing vibrio has never been cultivated from the 
blood. 

The changes in the intestines depend on the 
duration of the infection. In cases which prove 
fatal within a few hours the mucosa shows only 
moderate general reddening, which is intensified 
at the borders of Peyer's patches and the solitary 
follicles. The intestinal contents are of a rather 



CHOLERA. 311 

clear fluid nature in which are suspended flakes of 
mucus and epithelium; the fluid may be tinged 
with blood. With a longer duration the destructive 
processes in the mucosa become more intense, and 
consist largely of desquamation of the superficial 
epithelium and intense congestion of the denuded 
submucosa. In the more prolonged cases, "chol- 
era-typhoid," the mucosa, especially above the ileo- 
cecal valve, may show diphtheritic necrosis. The 
serous surface of the intestines is injected. 

The rational prophylaxis founded by Koch, on Prophylaxis. 
a knowledge of the biologic characteristics of the 
comma bacillus, has proved of great efficiency. 
The essential points are the following: 1. Imme- 
diate bacteriologic examination of the stools in 
suspicious cases. 2. Absolute isolation of patients, 
in a hospital whenever possible. 3. Thorough dis- 
infection of the stools, linen, room and all articles 
with which the patient has been in contact, includ- 
ing water-closets and privies. 4. Continued iso- 
lation during convalescence until the stools are 
free from vibrios. 5. Repeated bacteriologic ex- 
amination of the stools of those who have been in 
contact with cholera patients until their freedom 
from vibrios is assured. 6. Frequent examination 
of the water supply at different points in order to 
detect the occurrence of water infection. 7. In 
case water infection exists, exclusion of the water 
from all domestic uses, and the institution of 
means to rid the water of infection. This may be 
done in the case of infected wells, but in the case 
of large systems reconstruction may be necessary 
for future protection. Water for household use 
should be boiled. Kolle compares the conditions 
in Germany and Russia during the epidemic of 



312 INFECTION AND IMMUNITY. 

1892-4. In Germany, where Koch's principles of 
prophylaxis were rigidly observed, about 10,000 
cases occurred, 9,000 of which were confined to 
Hamburg, whereas in Eussia, where precautions 
were not enforced strictly or generally, 800,000 
cases developed during the same period. 
vaccination. Protective inoculation has shown itself to be of 
distinct value for prophylaxis. Ferran, a Span- 
iard, first practiced vaccination on a large scale in 
1884, although little definite knowledge of the 
value of the procedure resulted from his work. 
He is supposed to have used impure cultures. Haff- 
kine introduced protective inoculation on a large 
scale in India, and up to 1895 had inoculated 40,- 
000 persons. Following Pasteur's method with 
anthrax, he used two vaccines. Vaccine 1 was a 
culture which had been attenuated by prolonged 
growth at 39° C. Vaccine 2, which was adminis- 
tered five days later, was a virulent culture. The 
living organisms were used in both vaccines and 
the injections were given subcutaneously. The 
local and general symptoms were mild. Instead 
of living cultures Kolle has proposed the use of 
virulent cultures which have been killed by expo- 
sure to a temperature of 58° C. for one hour. The 
vaccine is preserved by the addition of 0.5 per 
cent, phenol. In the Japanese epidemic of 1902 
this method was used on an extensive scale. The 
incidence of disease among the uninoculated was 
13 per cent., among the inoculated 0.06 per cent. ; 
the mortality among the uninoculated was 10 per 
cent., among the inoculated only 0.02 per cent. 
The disease, when it occurred in the inoculated, 
was of a mild type. A single injection of from 2 
to 4 mg. of a killed agar growth was given sub- 



CHOLERA. 313 

cutaneouslj (cited by Kolle). Strong has pro- 
posed the use of the products of autolysis of the 
cholera vibrio as a vaccinating substance, a method 
founded on the observations of Neisser and Shiga 
in relation to typhoid, and of Conradi and Drigal- 
ski in relation to dysentery. The local and general 
s}'mptoms are said to be of a mild type. The 
method has had no practical trial. 

From what was said above in connection with Natural im- 
munity and 
the so-called cholera carriers, it is evident that not Susceptibility. 

all are equally susceptible to infection with chol- 
era. In the few instances in which infection has 
been attempted deliberately, some contracted the 
disease, at least one case ending fatally, whereas in 
others either a mild infection or none at all took 
place. The conditions on which such cases of in- 
dividual immunity depend are not known conclu- 
sively, although it is often intimated in a general 
way that a strong bactericidal power of the body 
fluids, .or a high phagocytic power on the part of 
leucocytes, is responsible for it. The gastric juice, 
on account of its acidity, offers a barrier to the 
passage of living vibrios into the small intes- 
tines, and this is particularly true of cholera. 
It is nevertheless evident that the barrier in many 
instances is not a serious one. A number of cases 
are recorded in which investigators while working 
with cultures have become infected with cholera, 
the cases running typical courses which sometimes 
ended fatally (Pfeiffer, Pfuhl and others). Or- 
ganisms which are ingested with water may pass 
rapidly to the intestines without being affected by 
the acid of the stomach, or when taken with food 
they may be buried in the latter and hence not 
come in contact with the gastric secretion. It 



314 INFECTION AND IMMUNITY. 

seems probable that the intestinal epithelium has 
a certain resistance to invasion which is most mani- 
fest in the case of those who do not become in- 
fected in spite of the presence of the organisms in 
their intestines. Natural immunity appears to be 
one which is directed against the bacteria rather 
than against the endotoxin, proliferation of the 
organisms in the intestinal epithelium being pre- 
vented. Poorly nourished individuals, the very 
young and the very old are particularly suscepti- 
ble. Other gastrointestinal disorders, in the pres- 
ence of an epidemic, predispose to infection. De- 
fects in the intestinal epithelium, or a decreased 
resistance of the latter ( !), may afford favorable 
conditions for invasion. 
Acquired Active immunity, as that which results from in- 
fection or from protective inoculation, is charac- 
terized by the appearance of bactericidal ambocep- 
tors, agglutinins and specific precipitins in the 
serum. It is now widely believed that acquired im- 
munity depends on the presence of the bactericidal 
amboceptors in the circulation and body fluids, al- 
though Metchnikoff holds, on the other hand, that 
it depends largely on an increased phagocytic 
power on the part of the leucocytes. According to 
Pfeiffer and Marx, the antibodies are produced in 
the blood-forming organs. An attack of cholera 
confers immunity of prolonged duration, although 
it is not always absolute. 

Passive immunity is readily induced in animals 
by the injection of anticholera serum. As in other 
instances, it is of short duration. Doubtless the 
same condition may be induced in man. Besredka 
has proposed mixed active and passive immuniza- 
tion for protective inoculation, iisino- killed Inn- 



PLAGUE. 315 

teria which have been saturated with the specific 
amboceptors. 

Serum therapy has been no more successful in Serum 
cholera than in typhoid fever. The antitoxic Agglutination. 
serum of Eoux and others has had no practical 
trial. According to Achard and Bensaude, the 
serum of cholera patients, on the third or fourth 
day of the disease, agglutinates the cholera vibrio. 
However, they used the serum in dilutions of 1-20, 
and in this strength even normal human serum 
may be agglutinating (Pfeiifer and Kolle, cited by 
Paltauf). Convalescents even after seven months 
may show an agglutinating power of from 1/100 to 
1/120. 

The bacteriologic examination of the stools is 
the most reliable means of early diagnosis (see 
above). 

VII. PLAGUE. 

Plague was known in the second and third cen- 
turies. In the sixth century it ravaged the Eoman 
empire and destroyed half the population in the 
eastern provinces. Under the name of the "black 
death" it swept over Europe in 1347-50 with a 
sacrifice of one-fourth of the inhabitants — about 
25,000,000. During the fifteenth and sixteenth 
centuries many epidemics prevailed in various 
parts of Europe, and the disease seemed to have 
fastened itself on that part of the world. However, 
the pneumonic form of the disease, the most con- 
tagious, gradually became less common, or the vir- 
ulence of the infection diminished, and this, with 
the institution of quarantine regulations, decreased 
the prevalence of the plague during and following 
the seventeenth century. Xcvertheless, there have 
been occasional outbreaks in Eastern Europe since 



Characteristics 
of the Or- 



316 INFECTION AND IMMUNITY. 

that time. Following the recrudescence of plague 
in Hongkong in 1893 and in other places later, 
the disease has been subjected to. scientific study, 
its cause has been discovered, and the importance 
of rigid quarantine measures at seaports in pre- 
venting its universal extension has been proved. 
In the Hongkong epidemic of 1893-4 Kitasato 
ganism. an d Yersin, working independently, discovered the 
bacillus of plague, Bacillus pestis. The organism is 
minute (1.5 to 1.75 by 0.5 to 0.7 microns), and 
typically is of long oval shape. The frequent oc- 
currence of short oval cells (coccus form), longer 
rods and distorted, swollen, vacuole-like cells (in- 
volution or degeneration forms) signifies a high 
degree of pleomorphism which is characteristic. 
The longer the disease has lasted, or, on the other 
hand, the older the culture, the more numerous are 
the atypical forms. In bouillon long chains de- 
velop. It is non-motile, has no flagella and forms 
no spores. A capsule may be demonstrated by ap- 
propriate technic. It does not stain by Gram's 
method, and with methylene blue, carbol fuchsin, 
etc., the ends stain more densely than the central 
portion (polar staining). Because of its general 
properties it is placed in a group with a number of 
bacteria which cause hemorrhagic septicemias in 
various animals — the "hemorrhagic septicemia 
group." 

There occurs in bouillon the so-called "stalac- 
tite" growth, in which visible processes extend 
from the surface toward the bottom, where they 
meet other processes which extend toward the sur- 
face ("stalagmites"). These formations utilize as 
their starting points the side of the flask or drops of 
butter or oil which are placed on the surface. Cer- 



PLAGUE. 317 

tain other organisms grow in a similar manner. 
It is said to be a characteristic feature of the 
plague bacilli that many involution forms appear 
on agar which contains 3 per cent, of sodium 
chlorid. The optimum temperature for growth is 
from 25° to 30° C, which is somewhat lower than 
that for most pathogenic organisms. It grows 
rather slowly even under the best conditions. In 
mixed cultures it is overgrown by saprophytic or- 
ganisms (e. g., colon bacillus). 

The plague bacillus may live for from four to viability and 

a . ,! , p • j, • Resistance. 

seven days in the putreiymg organs oi man or ani- 
mals. Its virulence may be retained in the cadaver 
of a rat for two months (Bandi and Stagnitta- 
Balistreri). During this time the organisms pene- 
trate all the tissues of the body, even growing 
through the skin. It may live in the pus of a 
bubo for twenty days when unmixed with other 
organisms (Albrecht and Gohn) ; in the sputum 
from plague pneumonia for ten days; in various 
foods, as milk, potatoes, for one to three weeks ; in 
water from five to twenty days, depending on the 
number of saprophytes which are present; in earth 
from two weeks to three months, depending on the 
quantity of organic matter and other organisms. 
In all these instances the higher the temperature, 
i. e., above 30° C, and the more numerous the 
saprophytic organisms, the shorter is the life of 
the plague bacillus. In winter, when contaminat- 
ing saprophytes grow less rapidly, the plague bacil- 
lus lives longer. Its resistance to desiccation, sun- 
light and disinfecting agents is rather low, par- 
ticularly when the surrounding temperature is 
above 30° C. In temperatures of from 29° to 31° 
C, when thoroughly dried, it rarely lives longer 



318 INFECTION AND IMMUNITY. 

than from six to seven days, whereas at lower tem- 
peratures, 16° to 20° C, cultures may be obtained 
after from one to several weeks, depending on the 
material which contains the organisms. It lives 
longer in woolen and cotton threads (clothing) 
than when isolated as in dust ; hence, dust infection 
is improbable (Dieudonne). In sputum (plague 
pneumonia) and purulent exudates in which the 
bacilli become incrusted to a degree, life may per- 
sist for from three to four weeks. Sunlight kills 
them in from two to six hours, depending on the 
temperature and the proximity of the organisms to 
the surface. Although cultures for the purpose of 
vaccination have been killed at a temperature of 
05° C. for one hour, precautions to insure an even 
distribution of the heat are necessary to render cer- 
tain the death of all organisms. A temperature of 
100° C. kills them at once, and 80° C. in from five 
to ten minutes (moist heat) . They are very resis- 
tant to cold, remaining alive at a temperature of 
— 20° C. for several weeks, even when repeatedly 
thawed out during this time, and they even prolif- 
erate slowly at from 4° to 7° C. 
virulence Cultures of the plague bacillus retain their viru- 
lence over a long period when kept in a cool dark 
place and when not allowed to dry. However, 
they often loose in virulence unaccountably. The 
nature of the toxic substance is as yet obscure. A 
concentrated soluble toxin has never been obtained 
in cultures. Filtrates of young cultures show lit- 
tle or no toxicity, whereas in older cultures the 
fluid becomes more or less toxic (liberation of en- 
dotoxin?). Lustig and Galeotti extract cultures 
with 0.75 to 1 per cent, potassium hydroxid, from 
which they precipitate a toxic substance with ace- 



and Toxins. 



PLAGUE. 319 

tic or hydrochloric acid. Markl found the cell 
bodies to be very toxic after eight weeks' growth at 
room temperature, provided the organisms were 
killed by chloroform rather than by heat; killing 
by heat destroys the toxic substance largely. He 
believes some metabolic product of the organism 
is the chief toxic constituent, claiming at the same 
time the presence of a certain amount of soluble 
toxin. 

The plague bacillus is exceedingly virulent for virulence 
rats, guinea-pigs and monkeys; somewhat less forAmma,s - 
virulent for mice and adult rabbits ; other animals, 
cats, dogs, swine, cows, horses, sheep, goats, may be 
infected artinciall} T , although they commonly re- 
cover even after large doses. Eats and guinea- 
pigs may be infected by subcutaneous, intraperito- 
neal and intravascular injections, by the feeding of 
infected material or by placing it on the nasal mu- 
cous membrane or in the conjunctival sac, and by 
inhalation experiments, the last method commonly 
resulting in plague pneumonia. Guinea-pigs and 
young rabbits die of plague septicemia in from 
four to five clays when cultures or material con- 
taining the organisms (sputum, feces, organs from 
plague cases), are rubbed into the shaven or even 
unshaven skin (Albrecht and Gohn). This experi- 
ment is of value for detecting virulent plague ba- 
cilli and separating them from contaminating or- 
ganisms. Following inoculation into a cutaneous 
or mucous surface a local reaction of varying in- 
tensity develops in which the subcutaneous tissue 
becomes edematous or even hemorrhagic, in a num- 
ber of hours the regional lymph glands become 
swollen and hemorrhagic, and in from two to five 
days the animals die of plague septicemia. Cul- 



320 



INFECTION AND IMMUNITY. 



Endemic 
Plague. 



Plague 
in Rats. 






tures of low virulence not infrequently cause a 
chronic infection which is characterized by the for- 
mation of large granulomatous nodules on the sur- 
face of the liver and spleen and in the omentum. 
Such foci contain many plague bacilli, and the 
death of the animal results in a few weeks from 
intoxication or from general infection. Although 
rabbits are much less susceptible than rats or 
guinea-pigs, young animals succumb to cutaneous 
inoculation. 

Dieudonne cites four foci in which plague is 
known to be endemic at the present time: One is 
in China (province of Yunnan), from which the 
Hongkong epidemic originated; a second in the 
Himalayas, which led to the outbreak in Bombay; 
a third in a mountainous region south of Mecca, 
and a fourth was found by Koch and Zupitza in 
British East Africa near the source of the White 
Nile. 

The opinion is held by many that plague is pri- 
marily a disease of the rat and that certain regions 
remain pest-infected because of this fact. Eats, in 
certain districts, suffer from a chronic form of the 
disease, and it is possible that the organism at 
times acquires increased virulence, as a conse- 
quence of which the infection becomes widespread 
and rapidly fatal among these animals. It is prob- 
able that the chief method of transmission from 
rat to rat is through the eating of plague cadavers. 
The possibility of transmission from one animal 
to another by means of fleas is upheld by some. 
The blood which fleas suck from infected rats fre- 
quently contains bacilli, but transmission to other 
rats by the bites of fleas is still disputed. 

The means by which the disease extends from 



PLAGUE. 321 

rat to man are not definitely determined. This 
much is known, however: First, that the bacilli 
are excreted in the urine and feces of infected ani- 
mals, and, second, that the disease attacks those Houses. 
especially who live in dark, damp, filthy quarters 
in which rats are numerous. Europeans who live 
under hygenic conditions in plague-infected dis- 
tricts rarely contract the disease. A great mor- 
tality among the rats not uncommonly precedes an 
outbreak of plague in man. The existence of 
"plague houses" may depend on the prevalence of 
the disease among the rats which infest the houses. 
On the other hand, the organisms excreted by a 
plague patient through the sputum, urine or feces, 
find, in the conditions described above, surround- 
ings which favor their prolonged life; hence, the 
occurrence of subsequent infection in the same 
house in many instances may be traceable to a pre- 
vious case. 

The theory has been advanced also that fleas Fleas. 
may be an important means of transferring plague 
from rats to man. This is objected to on the 
ground that every animal has its peculiar flea and 
that the flea of the rat will not bite man. Never- 
theless, it may alight on the skin of man tem- 
porarily and there discharge bacillus-laden excre- 
tions. Flies, in a like manner, may distribute the 
bacilli from rats or the infected excretions of man. 

When plague invades a new country it commonly 
makes its first appearance in coast cities. Pre- 
sumably this is accomplished through infected rats 
which may board a ship during its stay in a pest- 
ridden harbor, and which subsequently escape at 
the new port. 

Epidemics of plague lack the explosive-like sud- 



Infection 
Atria. 



322 INFECTION AND IMMUNITY. 

Epidemics, denness in their development which characterizes 
cholera and, to a certain extent, typhoid and dys- 
entery. The cases occur in groups and in particu- 
lar houses in such a manner that direct and indi- 
rect contact seem to be largely responsible for 
transmission. Every epidemic of plague may be 
divided into three stages : a slow progression from 
small centers, an acme of widespread death, and a 
slow recession (Dieudonne). It seems probable 
that the disease spreads rapidly and extensively 
only when the pneumonic form prevails. 

In man infection takes place through the skin 
most frequently, although the mucous membranes 
of the mouth, nose, pharynx, tonsils or the con- 
junctiva are possible infection atria. Often no 
local reaction is produced, and the point of en- 
trance may be indicated only in a general way by 
the swollen lymph glands of the region. Infre- 
quently a pustule or small carbuncle marks the 
point of entrance. Primary plague pneumonia is 
caused by the inhalation of pest-laden material, 
particularly fine particles of sputum from a pneu- 
monic case, and perhaps also by the inhalation of 
infected dust ; the latter is probably of less impor- 
tance because of the short life of the organism in 
dust. Even in ordinary speaking minute drops of 
saliva are thrown into the air. Infection is thought 
not to occur through the stomach or intestines. 
In the pneumonic and septicemic forms, the in- 
fected urine and feces contribute to the dissemina- 
tion of the organisms. Transmission by indirect 
contact, as by infected clothing and linen, has been 
noted in many instance?. Compared with pneu- 
monic and septicemic plague the bubonic form is 
much less dangerous to a community. 



PLAGUE. 323 

Following cutaneous infection the regional 
lymph glands become swollen and hemorrhagic, 
and undergo more or less extensive necrosis. When 
the infection extends beyond the lymph glands the 
blood may contain enormous quantities of bacilli 
(plague septicemia), and the same condition fol- 
lows plague pneumonia ; in the event of general in- 
fection death follows in a few hours. "Secondary 
pneumonia" and also "secondary buboes" develop 
as a consequence of blood infection. Hemorrhages 
into the mucous membrane (especially the stom- 
ach or cecum), endothelial surfaces (pericardium), 
and various parenchymatous organs, with extreme' 
degeneration of the latter (liver, kidneys and 
heart), are characteristic anatomic changes. The 
spleen is usually swollen. The toxic substance 
evidently has affinities for many tissues. 

Mixed infection with the streptococcus is not 
uncommon and is a serious complication. 

The following are important points for prophy- Prophylaxis. 
laxis: 1. Early diagnosis as established by bac- 
teriologic examination of blood, sputum, and fluid 
taken from a bubo either by a syringe or after in- 
cision ; 2, in the thorough isolation of patients and 
of those whose have been exposed to infection; 3, 
in the disinfection of excretions, of clothing and of 
infected houses, which in some instances may 
mean the destruction of the latter; 4, in the de- 
struction of rats; 5, prophylactic injections. Up 
to the present time the most effective measure of 
getting rid of rats is to offer a bounty for each 
animal caught, as practiced in Manila. 

The vaccine of Haffkine has been used exten- vaccines 
sively in India. The Indian plague commission 
found that the incidence of disease and the mor- 



324 INFECTION AND IMMUNITY. 

tality were lower among the inoculated than the 
uninoculated, although many of the inoculated 
contracted the disease in a benign form. The vac- 
cine consists of bouillon cultures which have grown 
for six weeks with stalactite formation (see above), 
then killed by exposure to a temperature of 65° C. 
for one hour; from 0.5 to 3.5 c.c. are injected, ac- 
cording to the age and size of the individual. One 
or more subsequent injections may be given. The 
local and general reactions are of moderate sever- 
ity. Protection becomes manifest only several 
days after the inoculation and may persist for 
many weeks or months. The vaccine recommended 
by the German commission consists of two days' 
old agar cultures which have been killed by heat 
(65° C. for one hour). Lustig and Galeotti utilize 
the toxic precipitate described above as a vaccine. 
Terni and Bandi inoculate rabbits or guinea-pigs 
intraperitoneally with the plague bacillus and 
after or just preceding death collect the peritoneal 
exudate, in which the organisms are allowed to pro- 
liferate still further for twelve hours. The bacilli 
are then killed at a low temperature, and this 
fluid, after an addition of a preservative, consti- 
tutes their vaccine. Although the last three vac- 
cines have proved of value in animal experiments, 
they have not as yet been used extensively in man. 

Besredka, also Shiga, recommend the use of 
mixed active and passive immunization, as sug- 
gested in relation to typhoid and cholera, in this in- 
stance naturally using plague bacilli (killed) and 
anti-plague serum. Shiga reported good results 
by the use of* the combined method in the epidemic 
in Kobe. 

The immunity which is produced by protective 



PLAGUE. 325 

inoculation, like that which follows natural infec- immunity. 
tion, is considered to be antibacterial inasmuch as 
the serum acquires increased bactericidal power for 
the bacillus, but shows no ability to neutralize its 
toxic constituents. As in relation to many other 
infections, however, we are not in position to ig- 
nore the possibility of an increased phagocytic 
power on the part of the leucocytes. The influence 
of opsonins is essential for experimental phago- 
cytosis. Wright characterizes the plague bacillus 
as "an organism which is absolutely insensible to 
the bactericidal action of the normal human blood 
fluids, but eminently sensible to the opsonic action 
of these fluids." The immunity which follows in- 
fection is of long duration. 

Prophylactic injections of antiplague serum pro- Serumtherapy 
duce a temporary immunity of about two weeks' f a n xis. r ° P v " 
duration. The Pasteur Institute prepares the 
serum of Yersin by immunizing horses first with 
killed and then with living cultures. The immun- 
ization is difficult and from several months to a 
year and a half are required for the production of 
a strong serum. When the blood is drawn eventu- 
ally its freedom from living plague bacilli and 
from toxic substances must be assured. The im- 
munizing value of the serum is determined by that 
quantity which will save a mouse from a fatal dose 
of living plague bacilli, the serum being given 
twenty-four hours in advance of the culture. This 
is accomplished by 0.1 to 0.02 c.c, depending on 
the strength of the serum. Its curative power is 
estimated from that quantity, 0.5 to 0.1 c.c, 
which saves a mouse when administered sixteen 
hours after the injection of an otherwise fatal dose 
of culture. For protective inoculation in man 



326 INFECTION AND IMMUNITY. 

from 10 to 20 c.c. are recommended, and for cura- 
tive purposes from 30 to 50 c.c. Concerning the 
value of this serum Dieudonne concludes as fol- 
lows: "On the basis of the results obtained in 
man and in animal experiments we can attribute 
no positive curative value to the Parisian serum, 
although a certain influence on the course of the 
disease can not be denied. On the other hand, the 
serum is suitable for protective inoculation when 
immediate immunity is necessary, as for those who 
are caring for cases of plague pneumonia. Since, 
however, the protection afforded by this means per- 
sists only for a few days, subsequent active immun- 
ization with killed cultures is indicated as soon as 
possible for those persons who are exposed to in- 
fection for some time." The favorable results 
noted by a number of observers would seem to jus- 
tify further use of the serum for curative pur- 
poses. 

The serum of Tavel, prepared at the Institute 
of Bern, is, like that of Yersin, bactericidal and 
agglutinating. Antitoxic as well as bactericidal 
properties are claimed for the serum of Lustig, 
which is prepared by immunization with the toxic 
precipitate mentioned above. It has been used ex- 
tensively in the treatment of plague and in a num- 
ber of small epidemics favorable though not thor- 
oughly convincing results were reported. The 
serum of Markl, which is supposed to be antitoxic, 
has had no practical trial. It is prepared by im- 
munization with old cultures which have been 
killed by chloroform. 
Agglutination. Although the serum of patients acquires a cer- 
tain agglutinating power, it is rather low (1/3 or 
1/5), and does not become manifest until during 



ANTHRAX. 327 

the second week of the disease. Before this time 
diagnosis by clinical or bacteriologic means can be 
made with certainty; hence, for clinical diagnosis 
the reaction has little value. On the other hand, 
a strong artificial agglutinating serum obtained 
by the specific immunization of animals is of great 
value for the identification of the plague bacillus 
when cultures have been obtained from suspected 
cases. Artificial serums may agglutinate in dilu- 
tions of from 1/1000 to 1/6000. 

B. Serum in acquired immunity is not bacteri- 
cidal, or knowledge on this point is deficient. 

I. ANTHRAX. 

From the standpoint of infection and immunity 
anthrax is of particular interest. It is the first 
disease of which the bacterial etiology was proved 
and in which the specific microbe was used in pure 
culture for the production of artificial immunity 
(vaccination). 

Anthrax is particularly a disease of cattle and 
sheep, and it prevails in certain European coun- 
tries, especially Eussia, in Australia and in South 
America. It does not occur extensively in this 
country. Definite regions are at times heavily in- 
fected, and it is in such localities that the disease 
is most frequently transmitted to man. 

As early as 1850 Rayer and Devaine, also Pol- Bacillus. 
lender, had discovered the presence of small rods 
and filaments in the blood of animals which had 
died of anthrax, and the work of Koch, Pasteur 
and others soon established that this rod, the anth- 
rax bacillus, is the cause of anthrax. The discov- 
ery of Koch that the bacillus forms extremely re- 



328 INFECTION AND IMMUNITY. 

sistant spores, explained the persistence with which 
the disease infects particular localities. 
spores. The anthrax bacillus is a fairly large organism, 
is rod-shaped, non-motile and grows with charac- 
teristic appearances on various culture media. 
With the proper temperature and culture medium, 
and in the presence of free oxygen, the formation 
of spores begins after about twenty-four hours of 
growth. Their evolution is complete in from one 
to two days, and eventually the protoplasm of the 
cells disintegrates and the spores are set free. 
Spores are not formed in the body of an infected 
animal. Spore formation is not essential, how- 
ever, for the continued life of the organism; at 
high temperatures (42° C), and in the presence 
of minute amounts of acids and alkalis or of car- 
bolic acid, strains may be so altered that they lose 
permanently the ability to produce spores. Under 
favorable conditions the spores germinate com- 
pletely in from three-quarters to one and one-half 
hours (Grethe) by a process in which they lose 
their refractive appearance and assume first an 
oval and then a rod shape. In the body a capsule 
surrounds the bacillus, and it grows singly or in 
very short chains ; in culture media it is very diffi- 
cult to obtain capsules. The long threads which 
appear in culture media, especially bouillon, are 
not found in infected animals. 
Resistance The bacillus itself shows no unusual resistance, 
but its spores are more resistant than those of any 
other pathogenic bacterium. When dried on a 
thread they have been known to live for from ten 
to twelve years. Corrosive sublimate (1-2000) 
kills them in forty minutes (Fraenkel), and direct 
sunlight in about 100 hours (Momont). Bacillus 



and Virulence 



ANTHRAX. 329 

pyocyaneus, streptococci, staphylococci and the ba- 
cillus of Friedlander are said to antagonize its 
growth, and Eettger found that the dried B. prodi- 
giosus decreased the virulence of the organism for 
animals when the two were injected. 

The anthrax bacillus is remarkable for its infec- 
tiousness. A twenty-millionth of a loop of a viru- 
lent culture will cause a fatal infection in mice, 
guinea-pigs and rabbits, when given subcutaneous- 
ly. A systemic infection may be produced by feed- 
ing the spores or causing animals to inhale them. 
The gastric juice is able to kill the bacilli, but not 
the spores, which germinate after they reach the 
intestines. 

The organism is distributed by the excretions 
of diseased animals, and after their death the ad- 
jacent soil becomes heavily infected by the dis- 
charges which escape from the intestines and blad- 
der. In this situation the bacilli pass into the 
sporing stage, in which they remain viable and 
virulent for a long time. 

The infection of herds usually is accomplished infection 
by the ingestion of spores which have been distrib- 
uted in this way, the spores germinating, as de- 
scribed above, after they have reached the intes- 
tines. The disease may be primary in the skin in 
the form of malignant pustule. In man malignant 
pustule is the commonest type of infection, occur- 
ring especially among those who have to do with 
cattle and sheep. The bacilli, however, may gain 
entrance through the lungs as in the so-called 
"wool-sorter's" disease, which is caused by the in- 
halation of infected dust from the raw material. 

The generalized infection in all animals is rapid- 
ly fatal (one to three days), and the occurrence of 



330 INFECTION AND IMMUNITY. 

death is sometimes so sudden as to be called apo- 
plectiform; in man the mortality is about 50 per 
cent. Malignant pustule runs a more favorable 
course. 
Toxin. The general infections are marked by symptoms 
of intense intoxication and acute degenerative 
changes are produced in the parenchymatous or- 
gans. Massive numbers of the bacilli are found in 
the blood. Neither a soluble toxin nor an endo- 
toxin characteristic for the organism has been dem- 
onstrated up to the present time (Sobernheim), 
although there is abundant clinical and anatomic 
evidence of intense intoxication. The production 
of mechanical injuries by the large masses of ba- 
cilli in the circulation is doubtful. 
Prophylaxis Rational prophylaxis involves the proper dispo- 
sal of the bodies of animals which have died of 
anthrax, the exclusion of animals from fields 
known to be infected, suitable disinfection of stalls, 
and finally protective inoculation against the dis- 
ease. No part of the anthrax cadaver should be 
used for commercial purposes, because of the dan- 
ger of infecting those who work with the raw ma- 
terials. Cleanliness and the usual precautions 
against contagious diseases should be observed by 
those who are exposed to infection, bearing in mind 
that the disease may be transmitted by way of the 
lungs and alimentary tract, as well as by the skin. 
Natural It is probable that no disease is more perplexing 
Susc&pUbiSty. from the standpoint of immunity than anthrax. 
The variations in susceptibility and immunity 
among different animals are extreme: Guinea- 
pigs, rabbits and mice are probably more suscepti- 
ble than sheep and cattle ; compared with these the 
dog and rat are relatively immune, whereas fowls 



ANTHRAX. 331 

and cold-blooded animals can be infected with dif- 
ficulty. Although the microbe is readily killed by 
suitable serums (rabbit, e. g.), such an effect is not 
an index of immunit}^ The serum of the highly 
susceptible rabbit is strongly bactericidal in test- 
glass experiments, whereas that of the more resist- 
ant dog, or rat, has little or no bactericidal power. 
Because of this inconsistent relationship of the 
serum to immunity, and since the leucocytes have 
a high phagocytic power for the anthrax bacillus, 
Ptruschky, Frank and others agree with Metchni- 
koff in assigning variations in the natural immun- 
ity of different animals to variations in phago- 
cytic power. Bail and Pettersson, in extensive ex- 
perimental work, discovered conditions which, they 
believe, explain the lack of correspondence between 
serum properties and natural immunity. In the 
serum of the relatively immune dog and chicken 
they found bactericidal amboceptors but no com- 
plement; hence, the serum could show no bacteri- 
cidal action in the test-glass. If, however, leuco- 
cytes from the same animals were added to the 
serum, the latter became bactericidal. It may be 
assumed that in the course of infection the ambo- 
ceptors are activated by complement which is dis- 
charged from the leucocytes. The failure of the 
bactericidal substances of the rabbit's serum to 
protect the animal was ascribed to the ability of 
the tissues to absorb the amboceptors (cited from 
Sobernheim). Their work is of sufficient im- 
portance to demand repetition. 

Wright has shown the importance of the opsonins 
for phagocytosis of the anthrax bacillus. 

Recovery from spontaneous infection is said to 



332 



INFECTION AND IMMUNITY. 



confer a degree of immunity, which, however, is 
not permanent. 
vaccination. Artificial immunity may be produced by active 
or passive immunization. The first attempts at 
vaccination were made in 1880 by Toussaint, who 
injected the blood of infected animals after it had 
been heated to 55 degrees for ten minutes. The 
bacilli were thus attenuated, but they were able to 
form spores subsequently and vaccination was not 
always successful. Pasteur used two vaccines. Vac- 
cine I consisted of a culture which was attenuated 
by growth at 42° C, and which contained no 
spores. Vaccine II was a virulent culture, and was 
injected in from ten to fourteen days after vac- 
cine I. Its use is said to have caused a decrease 
in anthrax in heavily infected districts, with a con- 
sequent decrease of the disease in man. Various 
modifications of the vaccines of Pasteur have been 
devised by others, and they seem to be equally suc- 
cessful. In some instances killed bacilli and the 
products of bacterial growth have been used with 
less success. The Antkracase-Immunproteidin of 
Emmerich and Lowe is not of established value. 

Immune serum for therapeutic purposes is pre- 
pared by immunization, first with killed or atten- 
uated cultures and then with virulent strains. The 
two vaccines of Pasteur may be used. Although 
the serum has been shown to have fairly strong 
protective powers, it is of less value when used for 
curative purposes. It produces no effect after the 
blood stream has been invaded by the bacilli. Its 
greatest value is for the protection of herds when 
anthrax has declared itself. In man it has been 
used chiefly in the treatment of malignant pustule 
in which the prognosis, even without specific treat- 



Serum Therapy 
and Prophy- 
laxis. 



MALTA FEVER. 333 

merit, is not unfavorable. The best known serums 
are those of Sclavo, prepared from the goat and ass, 
of Mendez and Deutsch. The properties on which 
the value of the serums depends are unknown. So- 
bernheim is very positive in stating that the bac- 
tericidal power of an animaFs serum is not in- 
creased by immunization or infection, and the ex- 
istence of an antitoxin is not recognized. As in 
some other instances immunization may cause an 
increase in opsonins which would render the serum 
effective by its power to cause increased phagocy- 
tosis. 

The method of Sobernheim, that of mixed active M j xe d immuni- 
and passive immunization, seems to be successful g?ut?natk>n. Ag * 
as a proplrylactic measure. The vaccine consists 
of a mixture of antiserum and bacilli. Immune 
and even normal serums at times may agglutinate 
the anthrax bacillus, but the reaction is inconstant, 
and the ability of an immune serum to cause ag- 
glutination is no index of its protective power. Ag- 
glutination is somewhat difficult of determination 
because of the tendency of the bacillus to grow in 
the form of chains. 

II. MALTA FEVER. 

Malta, Mediterranean or undulant fever, discovered 
in the Island of Malta, is also seen among British 
troops at Gibraltar, and cases have been discovered 
in the Caribbean Sea, Porto Rico, in Hongkong and 
in Manila. Historically, it has been traced to the 
beginning of the nineteenth century, but it was 
first described as an independent disease by Mars- 
ten in 1859. It is said to be extending. The dis- 
ease usually runs a long course, which is somewhat 
typhoidal in character, and there may be one or 



334 INFECTION AND IMMUNITY. 

more relapses. The spleen is enlarged, but the in- 
testines are not involved. 

"It is distinguished from typhoid by its long du- 
ration, sometimes extending over many months; 
by a course of fever exhibiting marked undula- 
tions; by the occurrence of copious perspirations; 
by the frequent appearance of rheumatic articular 
disorders as well as by neuralgia and inflammation 
of the scrotum and epididymis" (Scheube). It 
occurs especially in the summer months. 

Basset-Smith found the serum in practically all 
stages of the disease and in convalescence to have 
little or no bactericidal power for the coccus. Nor- 
mal serum appeared to be more bactericidal than 
that of the patients, although such an action was 
often missed in normal serum. Wright says that 
normal human serum is devoid of bactericidal 
power for the organism. Basset-Smith also con- 
cluded that the phagocytic power of the patient's 
leucocytes is less than in the case of normal leuco- 
cytes. According to Wright, the organism "is em- 
inently sensible to the opsonic action of the nor- 
mal serum," under the influence of which it is 
taken up in large numbers by the leucocytes. 

Agglutination by the serums of patients takes 
place in dilutions varying from 1-300 to 1-2000 
or even as high as 1-6000. Agglutinins develop 
fairly early in the course of the infection, and the 
test is of great diagnostic importance. 

Bacillus melitensis, discovered by Bruce (1887) 
in the spleen of patients who had died of the dis- 
ease, is a minute organism, slightly oval in shape. 
According to Gordon, it possesses one flagellum, 
rarely two or four, and is slightly motile. The 
bacillus is found in pure cultures in the spleen, 



MALTA FEVER. 335 

which is greatly enlarged. Its growth in culture 
media is very slow. 

It is thought that infected water may be one 
means of transmission of the disease. Laboratory 
infections have occurred through small wounds. 
The disease is not transmitted from person to per- 
son. 

Up to the present time the monkey is the only 
animal known to be susceptible to artificial infec- 
tion, although the organism may have a low degree 
of virulence for rabbits and guinea-pigs (Durham). 

One attack confers immunity, which may disap- 
pear, however, after some time (Hughes). 

An immune serum which was prepared by 
Wright is said to influence favorably the course of 
the disease. 



GROUP III. 



Acute infectious diseases in which acquired im- 
munity of prolonged duration is not established. 
In some instances soluble toxins are produced 
which are of unknown importance in infection 
(staphylococcus, streptococcus). Some of the or- 
ganisms contain rather strong endotoxins (pneu- 
mococcus, gonococcus), whereas in others a reason- 
able basis for their infectiousness is not at hand. 
In some instances immunization causes increased 
resistance to infection (staphylococcus, streptococ- 
cus), whereas this property has not been fully 
demonstrated in others.* The serums of immun- 
ized animals may or may not be protective for 
other animals. Those organisms which cause sys- 
temic infection give rise to clinical leucocytosis 
(except influenza). Local inflammations are ac- 
companied by the accumulation of polymorphonu- 
clear leucocytes. 

I. PNEUMOCOCCUS INFECTIONS — PNEUMONIA. 

Organisms No one organism is the exclusive cause of any 
Pneumonia* one type of pneumonia, except perhaps the viruses 
of syphilis and tuberculosis. Any microbe which 
causes pneumonia can also set up inflammations 
in other organs. The following may cause acute 
pulmonitis: Diplococcus pneumoniae, Streptococ- 
cus pyogenes, Staphylococcus pyogenes, bacillus of 
Friedlander (B. pneumoniae), B. influenza, B. pes- 
tis, B. diphtherice, B. typhosus, B. coli communis, 

* This point is difficult of determination when an organ- 
Ism has little or no pathogenicity for animals (influenza, 
gonococcus, bacillus of Ducrey, etc.). 



PNEUMOCOCCUS. 



337 



Diplococcus 






and Micrococcus catarrlialis. The organisms of 
tuberculosis, actinomycosis, the virus of syphilis 
and some other infections cause chronic inflamma- 
tions of the lungs. Some of these organisms have 
already been considered and others will be dis- 
cussed later, in their relation to pneumonia, with- 
out, however, entering into details as to the vari- 
ous types of the disease. The Diplococcus pneu- 
moniae is the commonest cause of lobar pneumonia. 
It produces lobular pneumonia not infrequently, 
and has been found* as the only organism in acute 
interstitial pneumonia (Weichselbaum). 

Friedlander (1882) found that capsulated cocci 
were present constantly in the exudate of pneumo- 
nia. Such cocci in all probability represented the 
organism which at present is known as the diplo- 
coccus of pneumonia, yet the cultures which he ob- 
tained somewhat later showed the characteristics 
of the organism now known as the bacillus of 
Friedlander. Fraenkel, in 1884, obtained the first- 
named coccus in pure culture, and his investiga- 
tions, together with those of Weichselbaum and 
many others, eventually established the independ- 
ence of the two organisms. 

The typical pneumococcus is slightly elongated, Typical and 
and both in the tissues and in culture media it stra[ns. ,ca ' 
grows in pairs. Typically, also, the pair possesses 
a capsule which is present constantly in the tissues 
and may be obtained on certain culture media 
(milk and serum). It is non-motile, non-flagel- 
lated, forms no spores and stains by Gram's meth- 
od. Eather scant growth occurs on the ordinary 
culture media in the form of small colonies which 
resemble those of the streptococcus, and unless spe- 
cial media are used it usually can not be carried 



338 



INFECT 10 X AXD IMMUNITY. 



Confusion with 
Streptococcus. 



Resistance. 



through many generations. When grown in spu- 
tum, or on a medium which contains ascitic fluid, 
the blood or serum of man or some favorable ani- 
mal, its virulence may be preserved for some time. 
By growth at 39° C. virulence is lost rapidly. 
Strains which are atypical in one of several ways 
are encountered. They* may show low virulence, 
may grow well at ordinary temperatures (the typi- 
cal organism not doing so), may produce long 
chains in liquid media, or may grow without a 
capsule. 

Recently the danger of confusing the pneumo- 
coccus with the streptococcus has received renewed 
attention, and newer methods of differentiation 
render it extremely probable that such confusion 
has occurred in the past. An important differen- 
tial method is that of cultivation on agar plates 
which contain blood (Schottmiiller) ; the strepto- 
coccus produces a clear zone of hemolvzed corpus- 
cles about its colonies, whereas the colonies of the 
pneumococcus present a greenish color and produce 
no hemolysis. In using this test Ruediger found a 
surprising number of pneumococci in normal 
throats, whereas previous work had shown them to 
be much less common than streptococci. 

In spite of the poor viability of the organism on 
ordinary culture media, it is fairly resistant to 
desiccation and sunlight, especially when imbedded 
in sputum. It is possible that the surrounding spu- 
tum is protective and that the well-formed capsule 
which the coccus possesses as a parasite, increases its 
resistance. When dried and powdered it is much 
less resistant, being killed by direct sunlight in 
about an hour. Like other bacteria, it resists dif- 
fuse sunlight better than direct, and in the former 



PNEUMOCOCCUS. 



339 



may live for as long as fifty-five days in a dried 
state (Bordoni-ITffreduzzi, cited by Weichsel- 
baum) . It has very little resistance to heat, being 
killed by a temperature of 52° C. for ten minutes. 

Xo characteristic soluble toxin has been obtained, 
although more or less poisonous substances, some 
of them of a chemical nature, have been described. 
Presumably the toxic properties reside in an endo- 
toxin. The pneumotoxin of F. and G-. Klemperer 
was prepared by precipitation with alcohol. The 
pneumococcus is a pyogenic organism and causes 
exudates which are rich in fibrin. Occasionally 
serous rather than purulent exudates are produced. 
Its toxic action is directed toward various organs, 
and it is doubtful if any of the tissues of the body 
are non-susceptible. Some strains are supposed to 
be more neurotoxic than others. 

The susceptibility of animals varies greatly. 
Rabbits and mice are extremely susceptible and are 
used as test animals for the identification of the 
organism. Other laboratory animals have greater 
resistance, and the pigeon and chicken are almost 
absolutely immune. In susceptible animals a rap- 
idly fatal coccemia or more or less extensive local 
lesions are produced, depending on the virulence of 
the culture, the seat of inoculation and the suscep- 
tibility of the animal. In rabbits lobar pneumonia 
has been produced by inoculation into the pleura, 
trachea, blood stream or subcutaneous tissue. 

The pneumococcus is present in the nose, mouth 
and pharynx of a large percentage of individuals. 
It is encountered more frequently in crowded cities 
than in country districts. It persists for weeks 
and months in the mouths of convalescents from 
pneumonia, and it reaches the mouths of those 



Toxic 
Properties. 



Susceptibility 
of Animals. 



Occurrence 
in the Body 



the Lungs. 



340 INFECTION AND IMMUNITY. 

who are in the vicinity of pneumonias. It is found 
frequently in the conjunctiva and occasionally in 
the deeper air passages. That it may reach the 
stomach and intestines with the sputum is appar- 
ent, and it has been found there as the cause of 
diphtheritic enteritis, a condition which may be 
followed by pneumococcus peritonitis or general 
infection. 
Entrance into The lungs are infected by inhalation of the 
cocci. Suspended in droplets of saliva or mucus, 
or adherent to foreign particles, they may be car- 
ried fairly deeply into the bronchial tubes. That 
they ever reach the alveoli by this means alone is 
questioned by many. Two factors would seem to 
prevent their being carried to the alveoli by cur- 
rents of inspired air: First, foreign bodies or in- 
fected droplets are likely to strike and adhere to 
the walls of the respiratory passages before they 
have traversed a great length, and from this situa- 
tion may again be carried out by the action of the 
ciliated epithelium or coughing; the tortuous pas- 
sages of the nose and its hairs and moist surfaces 
arrest many micro-organisms. Second, the velocity 
of the inspired air is greatly reduced or is nil by 
the time the particles might have reached the 
alveoli, a condition which renders their arrest all 
the more probable. Nevertheless, pneumococci do 
reach the alveoli, and by some it is supposed that 
even in health they are carried there more or less 
constantly and are as constantly destroyed. Occa- 
sionally they have been found in the parenchyma- 
tous tissue of the lungs of individuals who have 
died of other than pneumococcal infections or of 
non-infectious diseases. In order to show that 
micro-organisms may be carried into the paren- 



PXEUUOCOCCUS. 



341 



chyma by inspiration Wenninger allowed animals 
to inhale a spray containing Micrococcus prodigio- 
sus, and killing the animals after one-half hour, 
was able to cultivate the coccus from the base of 
the lungs where only alveoli and the finest bron- 
chial branches were present (cited by Weichsel- 
baum). 

Various other agencies have been suggested by 
which the cocci may be carried to the parenchyma- 
tous tissue. For example, during the forced res- 
piratory efforts which accompany coughing they 
may be carried from the bronchial branches into 
the alveoli. Or the organisms having reached the 
bronchi, may be carried through the walls of the 
latter, perhaps by the leucocytes, and reach the 
alveoli directly through the lymph channels or 
after having caused infection in the peribronchial 
lymph glands. Others express the opinion that 
pneumonia follows blood infection in many or 
most instances, i. e., that the infection is hemato- 
genous, the cocci having reached the blood in some 
obscure manner. That the infection may be hema- 
togenous is shown by the occasional occurrence of 
pneumonia secondary to pneumococcus infection in 
other parts of the body. 

Knowing the fairly constant presence of pneu- 
mococci in the upper respiratory passages in the 
normal individual, it seems certain that some un- 
usual condition must arise to precipitate infection 
of the pulmonary tissue. Concerning the nature 
of these conditions, we have little but theories. 
They may rest either with the microbe or the in- 
dividual, or with both. The pneumococci which 
are normally on the mucous surfaces may undergo 
an increase in virulence, or more virulent organ- 



Lymphogenous 
and Hemato- 
genous In- 
fection. 



Conditions for 
Infection. 



Resistance. 



342 INFECTION AND IMMUNITY. 

isms from the outer world, or from pneumonic pa- 
tients, may be inhaled. The latter condition is an 
important one in relation to the contagiousness of 
pneumonia and the development of epidemics. 
Park and Williams found a larger percentage of 
virulent organisms in the sputum of pneumonics 
than in that of normal persons. It is possible that 
the pneumococcus in being passed from one patient 
to another undergoes an increase in virulence, sim- 
ilar to the increase which may be obtained by pass- 
ing bacteria through animals. 
Decrease of On the other hand, it is very probable that es- 
sential changes take place in the individual, 
changes which in some may cause the lowered re- 
sistance which is so often referred to as a condition 
for infection. Exposure to cold has long been 
known as an important predisposing factor, al- 
though we continue in ignorance of its precise 
effects. Animals are more susceptible to pneumo- 
coccus infection after artificial reduction of the 
body temperature. It is possible that a lowered 
body temperature may decrease antibacterial ac- 
tivities; that the activity of the bactericidal fer- 
ments of the plasma or of the leucocytes may be 
suppressed, or phagocytosis may be inhibited so 
that organisms which reach the bronchi and peri- 
bronchial lymphatic structures are allowed to pro- 
liferate. It is probable that in health the leuco- 
cytes continuously pass through the bronchial and 
alveolar walls where they may englobe foreign par- 
ticles (coal dust) or bacteria, and leucocytes are 
present on the mucous membranes of the mouth 
cavity. Following exposure and the reduction of 
the body temperature, or following the prolonged 
inspiration of cold air, the activity of the phago- 



PNEUMOCOGCUS. 343 

cytes may be inhibited so that cocci which reach 
these surfaces are not ingested and continue to 
proliferate, or the same conditions may decrease 
the exudation of the leucocytes from the vessels. 
It is possible also that the activity of the ciliated 
epithelium is reduced similarly so that the cocci 
are not so readily carried to the exterior. 

Extreme exposure is not always followed by other Predis- 
pneumonia, however, and not all cases of pneumo- pos,na actors - 
nia are preceded by exposure; many other condi- 
tions may predispose to infection, as a lowered 
resistance due to alcoholism, other infections or to 
non-infectious processes. That certain local con- 
ditions may favor infection is indicated by the fre- 
quency with which individuals with chronic tuber- 
culosis of the lungs die of pneumococcus pneumo- 
nia, and the development of the disease in areas 
of hypostatic congestion. Age is of influence. "To 
the sixth year the predisposition to pneumonia is 
marked; it diminishes to the fifteenth year, but 
then for each subsequent decade it increases" 
(Osier). The cause of these variations is not 
known, although the rise in later years may be 
associated with increased exposure. 

The conditions which predispose to infection are 
now the subject of active study in many labora- 
tories, and the commission which the Xew York 
Department of Health has established for the study 
of acute respiratory diseases has already made im- 
portant observations as to the prevalence and viru- 
lence of pneumococci. 

Many observers have found pneumococci in the complications. 
blood in a large percentage of the cases, and recent 
work by Rosenow indicates that the blood is prob- 
ablv infected in all cases at some stage of the dis- 



344 INFECTION AND IMMUNITY. 

ease. This being the case, the frequency with which 
pneumococcus infections occur in other organs as 
complications of pneumonia is readily understood. 
Pleuritis is present almost constantly, pericarditis 
frequently, and the peritoneal cavity is invaded not 
infrequently by way of the diaphragm, with general 
peritonitis as the occasional result. In pneumo- 
coccus pleuritis the exudate is frequently of a 
serous character. Endocarditis, meningitis and 
arthritis are frequent complications. Conjunctivi- 
tis, otitis media, cutaneous or subcutaneous infec- 
tions, intramuscular abscesses and osteomyelitis 
may develop. The kidneys and liver usually show 
acute degenerations. 

Diplococcus pneumonia occurs as a complication 
in typhoid, diphtheria, tuberculosis, influenza, ery- 
sipelas and other infections, the organism of the 
primary infection also being found in the lungs. 
Not infrequently staphylococci,, streptococci, Mi- 
crococcus catarrhalis, or the bacillus of Friedland- 
er, are found with the pneumococcus, the latter 
being the predominating organism. Eecent work 
from Phipps' Institute (Flick, Ravenell and Er- 
win) suggests that the pneumococcus may be an 
exciting cause of pulmonary hemorrhage in the 
tuberculous. 
Prophylaxis. Prophylactic measures are largely of an individ- 
ual character. One should not come in contact un- 
necessarily with those suffering from pneumonia. 
The susceptible should be guarded against expos- 
ure; pneumonia should be considered as a conta- 
gious disease, the cases isolated as such, the sputum 
disinfected, and rooms cleaned with moist antisep- 
tics rather than by dusting and sweeping; the sick 
room should be flooded with sunlight, and the 



PXEUMOCOCGUS. 



345 



Immunity and 

Susceptibility. 



Recovery. 



mouths of convalescents disinfected. Expectora- 
tion in public places should be limited. To what 
extent the dust-laden atmosphere which prevails 
in most of our large cities is a factor in causing 
pneumonia is unknown. Vaccination is not yet 
an established procedure. 

It is probable that the susceptibility of man 
varies greatly. Under equal conditions of expos- 
ure not all contract pneumonia, and an individual 
who eventually contracts the disease may have 
undergone many similar exposures previously. 
Klemperer introduced a culture of the pneumococ- 
cus which was virulent for rabbits under his skin 
without suffering more than temporary disturb- 
ance. 

Eecovery seems to indicate an acquired immun- 
ity or resistance which is by no means permanent, 
and often is of very short duration. One may have 
as many as eight or ten attacks of pneumonia, the 
intervals between attacks being from three to five 
years on the average (Griswolle). What the re- 
covery or acquired resistance depends on is un- 
known. The marked leucocytosis of pneumonia, 
and the known phagocytic power of the leucocytes 
for the diplococcus, suggest strongly the impor- 
tance of the leucocytes for recovery. The serums 
of convalescents and of immune animals show no 
increased bactericidal power for the organism, nor 
are they strikingly antitoxic. 

Beginning with Fraenkel (1886), many have 
shown the possibility of increasing the resistance a nd P opsonins 
of susceptible animals to the pneumococcus by in- 
jecting first dead or avirulent and then virulent 
cultures; in this way the subjects can be made to 
withstand many multiples of the minimum fatal 



Serum 



346 



INFECTION AND IMMUNITY. 



Phagocytosis. 



Serum Therapy 
and Agglu- 
tination. 



dose. Culture filtrates and precipitates (the pneu- 
motoxin of F. and G. Klemperer) have been used 
for similar purposes. The serum of immune ani- 
mals, and in some instances of convalescents, has 
been found to have a protective effect when in- 
jected into other animals, and by some a curative 
effect is claimed when the serum is given shortly 
after infection. Mennes made the interesting ob- 
servation that "normal leucocytes only become 
phagocytic toward pneumococci when they are lying 
in the serum of an animal immunized against this 
bacterium" (Muir and Kitchie). This action may 
have been due to the effect of the opsonins which 
Wright and Douglass have shown to be essential 
for the phagocytosis of pneumococci. According 
to Neufeld and Kimpau, antipneumococcus serum 
is not bactericidal, but through the influence of 
bacteriotropic substances (opsonins ? ) which it 
contains renders the cocci more susceptible to 
phagocytosis. 1 Likewise, Park and Williams found 
antipneumococcus serum from the sheep to be 
protective for mice and to stimulate phagocytosis. 
The correspondence between bacteriotropic action 
and protective power was variable, however, so 
that it did not appear certain that the protective 
power of the serum was due entirely to its influence 
on phagocytosis. We are, of course, not sure that 
events in the animal body correspond with those in 
the test-glass. 

Some of the serums which have been prepared 
have been used therapeutically in man. The re- 
sults have not been sufficiently satisfactory to put 



1. This bacteriotropic substance, according to Xeufeld, 
differs from the opsonin of Wright in" that it is not de- 
stroyed by low degrees of heat. 



PXEUMOCOCCUS. 



347 



them on a* good basis, although some favorable re- 
ports have been given. 

The serum of Boemer, which is best known at 
the present time, is obtained by immunizing dif- 
ferent kinds of animals with several strains of 
pneumococci. The receptor apparatus of different 
strains probably differ; hence, a serum obtained 
by immunization with several strains probably 
would be effective against a large variety of pneu- 
mococci. Furthermore, since different animals 
may respond to immunization with a given organ- 
ism by the formation of amboceptors with different 
complementophilous haptophores, a theoretical ad- 
vantage is to be gained by mixing immune serums 
from several animals. The amboceptors of one or 
more of the serums may be susceptible to activa- 
tion by the complement of the patient's body, 
whereas if only one serum were used the chance of 
such activation would be decreased. Passler, in 
summing up the results obtained in the treatment 
of 24 cases with this serum, finds the course of the 
disease shortened, the temperature reduced and a 
tendency to limit the extension of the disease to 
other parts of the lungs. 

The serum of pneumonic patients shows an in- 
creased agglutinating power for the pneumococcus. 
The maximum is reached at or near the time of 
crisis, but rarely has a higher value than 1 to 50 
to 1 to GO (Xeufeld, Rosenow). It disappears 
quickly after recovery. In immunized animals the 
agglutinating power may be pushed to much higher 
limits. Not all strains yield agglutinins equally, 
and not all are agglutinated equally by the same 
serum. According to Collins, pneumococci fall 
into different groups, depending on their agglu- 



Serum of 
Roemer. 



Agglutination. 



348 INFECTION AND IMMUNITY. 

tinable properties; the same author determined 
the presence of group agglutinins in an immune 
serum. Neufeld states that a virulent strains were 
not agglutinated by the serum of pneumonic pa- 
tients. 

OTHER INFECTIONS BY THE PNEUMO COCCUS. 

Complicating infections by the pneumococcus 
during the course of pneumonia were mentioned 
above. They may occur by way of the lymph 
channels, as in pleuritis, pericarditis and peritoni- 
tis (through the diaphragm), by continuous exten- 
sion, as in infection of the bronchi, nose and, per- 
haps, the middle ear, or as metastatic infections 
following the invasion of the blood stream by the 
organisms. It is undoubtedly in the last named 
manner that meningitis, endocarditis, arthritis, 
muscular and subcutaneous abscesses arise. 
Mode of Other infections by the pneumococcus occur in- 
dependent of the existence of pneumonia. Such 
conditions are alveolar abscesses, conjunctivitis, 
dachryocystitis, serpent ulcer of the cornea, in- 
flammation of the middle ear, meningitis, enteri- 
tis, rarely peritonitis, and pneumococcus septice- 
mia which may be complicated by infection in vari- 
ous organs. The eye is exposed to infection from 
without and the ear from the pharynx. Primary 
pneumococcus meningitis occurs both sporadically 
and epidemically, although the meningococcus is 
a more frequent cause. The organisms may gain 
entrance through the middle ear or nose, or 
through the circulation from a primary focus in 
another organ, perhaps an undiscovered focus. Pre- 
ceding and during meningitis the nose is not in- 
frequently the seat of pneumococcus rhinitis, and 



Infection. 



STREPTOCOCCUS. 349 

the organisms may be carried from the nose to the 
meninges by way of the lymph channels. The 
blood may be infected secondarily. Pnenmococcns 
meningitis is almost invariably fatal. The organ- 
ism causes chronic meningitis less frequently than 
the meningococcus. Infection of the peritoneum 
may follow an intestinal infection ; a pure pneumo- 
coccus infection of the peritoneum in the absence 
of pneumonia is extremely rare. Pneumococcus 
infections of the eye, ear, intestines and perito- 
neum are likely to be accompanied by other or- 
ganisms. 

Pneumococcus conjunctivitis occurs in epidemic 
form and the same precautions should be taken 
to limit it as for the limitation of. influenza con- 
junctivitis. 

Serpent ulcer of the eye, a progressive phage- 
denic process in the cornea, has the pneumococcus 
as its essential cause, although other organisms 
may be present. Eoemer treats the condition with 
an antipneumococcus serum and claims that he is 
able to arrest the process if the treatment is begun 
sufficiently early. The serum is injected beneath 
the conjunctiva. 

II. STREPTOCOCCI. 

When wound infections, cases of septicemia and Discovery of 
pyemia were first studied bacteriologically, various Pv °9 en,c Cocc * 
names were applied to certain cocci which were 
found. Such were the Microsporon septicum of 
Klebs and the Coccoiacteria septica of Billroth 
and others. Pasteur recognized such organisms 
and cultivated them at an early date, but Ogsten, 
in 1880 to 1884, using the newly-devised technic 
of Koch, was the first to recognize two sorts of 



350 INFECTION AND IMMUNITY. 

pyogenic cocci, to which he gave the names of strep- 
tococci and staphylococci. The former grew in the 
form of chains and the latter in clusters. In 1883 
Fehleisen obtained the streptococcus in pure cult- 
ures from cases of erysipelas. Eosenbach deter- 
mined more exactly the significance of streptococci 
in wound infections and septicemia,- and gave to 
the organism the name of- Streptococcus pyogenes. 
Morphology. The typical streptococcus is a spherical or 
spheroidal cell, about one micron in diameter, 
which grows in the form of chains of varying 
length. Division takes place in one direction, 
only. Variations in form, such as diplococcus-like 
cells in pairs or chains, or elongated cells resem- 
bling bacilli, represent accidental stages or anoma- 
lies in division. Streptococci commonly appear as 
diplococci in the blood and tissues of the infected. 
Unusually large cells may be involution forms. 
The difficulty of distinguishing the pneumococcus 
from the streptococcus has been mentioned. At 
one time it was thought that streptococci could 
be separated into those which grew in long. chains 
(8. long us) and those which produce short chains 
(S.orevis): Although these names are still used 
for convenience, they are not well grounded, since 
the length of the chains is not an inherent prop- 
erty; one form may be changed into the other by 
appropriate methods of cultivation. Similarly the 
S. erysipelatis of Fehleisen is not a specific or- 
ganism for erysipelas, since strains from other 
sources are able to cause experimental erysipelas 
in man. Streptococci growing in short chains may 
be cultivated from the normal mouth cavity and 
they are usually of low virulence for animals. On 
the other hand, /S'. longus is more often obtained 



STREPTOCOCCUS. 351 

from wound infections, septicemia and malignant 
tonsillitis. Capsulated strains of high virulence 
are occasionally found in the body. Ordinarily, 
however, streptococci are not surrounded by a cap- 
sule. The Streptococcus mucosus capsulatus may 
be a pneumococcus. Although streptococci are de- 
scribed which do not stain by Gram's method, those 
with which we are concerned invariably react posi- 
tively. Streptococci are never, motile, possess no 
flagellse and form no spores. 

Streptococci grow better in a neutral or slightly cultivation. 
alkaline medium than in one of acid reaction, but 
virulence is lost rapidly. They may be cultivated 
indefinitely in media which contain serum or 
ascitic fluid, but even here virulence disappears 
gradually; frequent transplantation is necessary. 
In bouillon those strains which produce short 
chains or grow as diplococci cause a diffuse cloud- 
ing of the medium, whereas those growing in long 
chains sink to the bottom, leaving a clear overly- 
ing fluid. Streptococci demand little oxygen, all 
are facultative anaerobes and some are said to be 
obligate anaerobes ; obligate anaerobes may be cul- 
tivated from the vagina and intestines. The 
optimum temperature for growth is 37° C. 

When dried, streptococci live for from ten days Resistance. 
to several weeks; they are destroyed more quickly 
in the presence of sunlight. Susceptibility to 
antiseptics depends on the nature of the medium 
in which they are suspended or imbedded. When 
unprotected by bouillon or other fluid they are 
killed in a few seconds by 1/1000 corrosive sub- 
limate and 3 per cent, carbolic acid (Fehleisen) ; 
when in bouillon, by 1/1500 corrosive sublimate 
and by 1/200 carbolic acid in fifteen minutes. Ly- 



352 INFECTION AND IMMUNITY. 

ing on a mucous surface, where they are imbedded 
in mucus or tissue fluids, they are protected 
against antiseptics to some extent. They are fairly 
resistant to heat, being destroyed by a temperature 
of 70° to 75° C. in one hour (v. Lingelsheim). 
virulence. Streptococci vary widely in their pathogenicity. 
Cultures which are entirely non-pathogenic for 
animals are frequently cultivated from nature and 
from man. As a rule, however, the long chains 
obtained from pathological processes in man are 
pathogenic for rabbits and mice. Their virulence 
is very labile, and by passage through suitable ani- 
mals (rabbit, mouse) it may be pushed to a very 
high point; in doing this, however, the original 
virulence of the culture undergoes modifications. 
For example, Marmorek so increased the virulence 
of one strain that the milliardth part of a c.c. was 
fatal for rabbits, but it had lost its pathogenicity 
for man, as shown by inoculations into carcino- 
matous patients. Hence the pathogenicity of cul- 
tures for animals is not a good index of their viru- 
lence for man. Those which produce long chains 
in bouillon are more pathogenic than those form- 
ing short chains (v. Lingelsheim) . 

Eabbits and mice are the most susceptible ani- 
mals. The rat, guinea-pig and cat, and larger ani- 
mals, as the horse, goat and sheep, are less sus- 
ceptible. A bouillon culture of which .01 to 1.0 
c.c. will kill a mouse or rabbit in from one to four 
days is considered of high to moderate virulence. 
Virulent cultures cause systemic infection, regard- 
less of the method of inoculation. Less virulent 
cultures produce changes which are more localized 
in character and which may heal: abscesses, areas 
of necrosis and erysipelatous inflammations. 



STREPTOCOCCUS. 



353 






The properties on which the virulence of strepto- Endotoxin. 
cocci depends are little understood. The conflict 
of opinion concerning many points probably de- 
pends on the use of different strains of the organ- 
ism in experimental work. The amount of endo- 
toxin which virulent strains contain is subject to 
great variations. Aronson found practically none 
in the killed cells of a very virulent strain. It 
seems probable that the endotoxin is rather sus- 
ceptible to heat, since cultures which are killed 
by mild methods, as by chloroform, are more toxic 
than those which are killed by heat. The filtrates 
of old bouillon cultures are more or less toxic. A 
strong "toxin" was prepared by Marmorek by 
growing a virulent strain in a mixture of serum 
and. bouillon for three - months and filtering the 
culture. More recently he uses a medium contain- 
ing glycocol and leucin. Toxic precipitates from 
fluid cultures have also been obtained. Bouillon 
filtrates of virulent cultures after two to fourteen 
days of growth have low toxicity (Aronson). 

Besredka, and later G-. F. Ruediger, showed that streptolysin 
virulent streptococci produce a hemolytic toxin joii, e . ucocyUc 
when grown in various heated serums. Euediger 
proved that this hemolysin (streptocolysin) is a 
true toxin, possessing a haptophorous and toxo- 
phorous structure. This discovery has an im- 
portant bearing on the fact that the blood in fatal 
streptococcus infections, especially in rabbits, is 
often more or less laked. Streptocolysin is de- 
stroyed by a temperature of 70° C. in two hours, 
by peptic digestion, deteriorates rapidly at ordi- 
nary temperatures, and is non-dialysable. Certain 
normal serums contain antistreptocolysin (Rue- 
diger). Another significant discovery by Eue- 



354 INFECTION AND IMMUNITY. 

diger is that virulent strains, when grown in serum 
and ascitic fluid, produce a substance which kills 
leucocytes and inhibits phagocytosis. This may 
explain the failure of leucocytes to take up virulent 
organisms, whereas non-virulent strains are readily 
phagocytized. Lingelsheim states that strains cul- 
tivated from subacute or chronic processes produce 
more soluble toxin (nature unknown) than highly 
virulent strains. Not all toxic filtrates contain 
streptocolysin, the hemolysin being independent of 
other toxic constituents (Simon). Lingelsheim 
concludes that the infectiousness of streptococci is 
not explained by the toxic properties which have 
been demonstrated. He lays stress on their resist- 
ance to the bactericidal activities of the tissues and 
tissue fluids. It is safe to say that up to the pres- 
ent time the essential toxin of the streptococcus 
has not been demonstrated. 
Pathologic Streptococci are the frequent cause of wound in- 

Processes 

f ections, the most common cause of lymphangitis 
and diffuse inflammations of the subcutaneous and 
intermuscular connective tissues (cellulitis), endo- 
metritis and puerperal septicemia, endocarditis 
and {onsillitis, are often the exciting organisms 
in pneumonia (lobular, usually), bronchitis, 
meningitis, inflammations of the serous surfaces 
(pericardium, pleura, peritoneum joints), enteritis 
and suppurative processes in the middle ear. They 
are the exclusive cause of erysipelas, which occurs 
naturally, and serious attempts have been made to 
show that they are etiologic factors in scarlet 
fever and rheumatic fever. The streptococcus is 
the most common organism found in the lesions 
of impetigo contagiosa, although it may be mixed 
with other bacteria, especially the staphylococcus. 



STREPTOCOCCUS. 355 

Occurring as mixed infections in pneumonia, tu- 
berculosis, scarlet fever, enteritis and other proc- 
esses, they cause grave and often fatal complica- 
tions. 

Xot all streptococci are able to cause erysipelas, Erysipelas. 
and a streptococcus cultivated from a case of ery- 
sipelas is not able to cause the disease in all indi- 
viduals. Furthermore, cultures obtained from 
other sources (phlegmon) may produce the dis- 
ease. (Koch and Petruschky.) Koch produced 
an erysipelatous inflammation with a staphylococ- 
cus. It has been suggested that streptococci which 
cause erysipelas, rather than some other process, 
do so because of some peculiarity in their virulence 
or in the resistance of the individual, or perhaps 
both. Another suggestion is that this type of in- 
fection depends on some peculiarity in the skin 
and subcutaneous tissue of the susceptible. The 
conditions are obscure. The infection atrium is 
not always known. In facial erysipelas entrance 
probably is gained through the mucous membrane 
of the nose in many instances. Erysipelas is a 
wound infection in most or all instances, although 
the atrium often escapes observation. The cocci 
lie principally in the lymph spaces and interspaces 
of the connective tissue. They are rarely to be 
cultivated from the scales or the fluid of blisters, 
but may be obtained from skin which is excised 
from the border of the inflamed area. (Fehleisen.) 
They probably are not excreted through the un- 
broken skin. 

Erysipelas is an inflammation of the superficial Lymphangitis. 
lymphatics of the skin, while in lymphangitis the 
deeper lymphatics are involved. Thrombosis of 
the lymphatic vessels, congestion of the adjacent 



356 INFECTION AND IMMUNITY. 

blood vessels, causing reddened streaks and local 
hemolysis (?), are distinguishing local features. 
Metastases occur to adjacent lymph glands and 
the infection may become general. In this process, 
as well as in wound infections, thrombosis of the 
adjacent vessels may occur, which may be the first 
step in the production of pyemia with multiple 
points of infection. Cellulitis may also be caused by 
the staphylococcus alone or infection with the lat- 
ter may be superimposed on a primary streptococ- 
cus cellulitis. 

Pneumonia. Pneumonia produced by the streptococcus may 
either be primary or secondary to infection in 
other parts of the body. Characteristically, it re- 
sembles the lobular type in the occurrence of 
multiple foci, which present a smooth surface on 
section and are very rich in cells. It occurs less 
frequently as the cause of lobar consolidation, and 
very frequently as a mixed infection in pneumo- 
nias caused by the pneumococcus and other organ- 
isms. Streptococcus infection of the lungs in pul- 
monary tuberculosis is a serious and frequent com- 
plication of the latter disease. It produces a septic 
condition, involves adjacent healthy tissue, and its 
role in causing consolidation and liquefaction of 
the tissues predisposes of hemorrhages. In cultures 
the streptococcus is said to inhibit the growth of 
the tubercle bacillus, and it has occasionally been 
noted that the tuberculous, after suffering a strep- 
tococcus infection (erysipelas), show an improved 
condition ! 

Meningitis. Primary streptococcus meningitis is rare or of 
doubtful occurrence. It frequently is secondary 
to otitis media, and has been noted following ton- 



STREPTOCOCCUS. 



357 



sillitis, facial erysipelas, pneumonia, endocarditis 
and as part of a pyemic process. 

Streptococci are perhaps the most important Enteritis. 
cause of enteritis in children, the inflammation 
often being membranous and accompanied by 
desquamation of the epithelium and by hemor- 
rhages. It is not infrequently followed by peri- 
tonitis and septicemia. Virulent organisms prob- 
ably reach the intestines through milk in many 
instances. Escherich found streptococci in nearly 
every sample of milk which he examined. Digest- 
ive disturbances due to other causes predispose to 
infection. The organisms are nearly always pres- 
ent in the intestines of the adult, but cause en- 
teritis less frequently than in children. 

The normal vagina does not offer a good cul- v a gina and 
lure medium for pathogenic bacteria, although uteru »* 
streptococci are occasionally found there. They 
occur more frequently in those who have borne 
children. The vagina tends to purify itself me- 
chanically and by the acid nature of its secretions. 
If the secretion for any reason becomes alkaline, 
as in catarrhal conditions, or if it contains blood 
and serum, which provide a good culture medium, 
virulent streptococci proliferate. Infection takes 
place through denuded surfaces and tears ; endome- 
tritis, metritis, parametritis, salpingitis, peri- 
tonitis and sepsis may follow. Thrombosis of the 
blood vessels may be followed by the development 
of pneumonic foci. 

Streptococci are probably always present on the Upper Respira- 
tonsils, the mucous membrane of the mouth, very orv assa9es - 
frequently in the sputum and not infrequently on 
the mucous membrane of the anterior nares.. Pre- 
sumably they proliferate under inflammatory con- 



358 INFECTION AND IMMUNITY. 

ditions from whatever cause, finding in the serum 
and -plasma which exude a medium favorable for 
growth and the development of virulence. They 
are of great significance in severe local inflamma- 
tions, as in diphtheria and scarlatina, and when 
general resistance is lowered, as in typhoid, typhus, 
variola, measles, etc. Lingelsheim characterizes 
their relation to diphtheria as follows : they injure 
the tissues locally, penetrate beneath the mem- 
brane into the tissues and take part in the forma- 
tion of the membrane; they increase the virulence 
of the diphtheria bacillus ; alone, or in conjunction 
with the diphtheria bacillus, they may invade the 
lungs, causing bronchopneumonia, or enter the 
circulation and injure various organs, but particu- 
larly the kidneys. Their method of entering the 
lungs from the upper respiratory passages probably 
is similar to that involved in pneumococcus infec- 
tion. Furthermore, having obtained a footing 
in the pharynx, for example, they may reach the 
bronchi and perhaps the alveoli by extension along 
the surface. 

Streptococci are usually the essential organisms 
in follicular tonsillitis, are frequently found in 
alveolar abscesses, but in both instances may be 
mixed with other organisms, especially the staphy- 
lococcus and pneumococcus. Streptococci in the 
throat may appear in diplococcus form in fresh 
preparations. Beginning primarily in the nose, 
tonsils or pharynx, streptococcus infection may 
extend to the adjacent sinuses, the middle ear, 
meninges, or through the tonsils may cause sys- 
temic infection with endocarditis as a frequent 
complication. 

The endocarditis caused by streptococci usually 



Rheumatic 



STREPTOCOCCUS. 359 

is vegetative in character, but may be ulcerative, Endocarditis. 
and may result in metastatic foci of infection 
(e. g., septic infarcts). Infarcts from strepto- 
coccus endocarditis are not always infected, how- 
ever. Not infrequently the vegetations contain 
staphylococci as well as streptococci. 

Since 1867, when Salisbury described a fungus 
which he called Zymoiosis translucens, many micro- fever. 
organisms have been described and cultivated from 
the joints, blood, endocarditic and pericarditic 
lesions and from the tonsils in acute articular 
rheumatism. Among them were the "Monadinen" 
of Klebs (1875), short bacilli by Wilson (1885) 
and others, staphylococci and streptococci by 
Weichselbaum (1885) and by many others, and 
an anaerobic bacillus resembling that of anthrax 
by Achalme (1890). Streptococci have been found 
more frequently than other organisms. The ba- 
cillus of Achalme acquired considerable prominence 
at one time, being found in rheumatism in a num- 
ber of cases, but it has been found since in other 
conditions, and normally, and Achalme himself 
gave up his original claims for its etiologic 
significance. The organism, possibly, is identical 
with B. aerogenes capsulatus of Welch (Harris). 
Many of the observations are of little value, since 
the cultures were made postmortem, when contami- 
nations and agonal invasions by other organisms 
could not be excluded. The conditions were very 
confusing, however, since the injection of pure 
cultures occasionally produced arthritis, peri- 
carditis and endocarditis in animals. This was 
the case with a short anaerobic bacillus or diplo- 
bacillus cultivated by Thiroloix, and by Triboulet, 
Coyon and Zadoc (1897). 



360 INFECTION AND IMMUNITY. 

In 1897-98 Triboulet and Coyon cultivated from 
the blood of five cases of rheumatic fever a diplo- 
coccus, pure cultures of which caused arthritis, 
endocarditis, etc., in rabbits. Similar observations 
have been made by Westphal, Wassermann and 
Malkoff, Poynton and Paine, Beaton and Walker 
and others, and the possibility of producing lesions 
characteristic of rheumatic fever by the inocula- 
tion of pure cultures into rabbits has been well es- 
tablished. Although the organism was called a 
diplococcus by the discoverers, it can not be dis- 
tinguished from the ordinary streptococcus pyo- 
genes by cultural tests. These discoveries do not, 
however, put this particular streptococcus on a 
satisfactory basis as the cause of the disease, since 
streptococci from various sources are able to cause 
experimental arthritis in rabbits (Cole, Harris). 
It seems that virulent streptococci from whatever 
source have a predilection for serous surfaces. This 
is apparent from the frequency with which the 
joints, endocardium, etc., are involved in strepto- 
coccus septicemia in man. The view of Singer 
and of Menzer that "acute rheumatism is simply 
one of the many manifestations of streptococcus 
invasion" (Harris), finds some justification in 
the streptococcus tonsillitis with which the dis- 
ease usually begins, the recovery of streptococci 
from the lesions and the production of these lesions 
in rabbits by the injection of pure cultures. The 
fact remains, however, that streptococci can not 
always be cultivated from the lesions of rheumatic 
fever \ hence it is possible that the organism may 
exist as a mixed infection with more or less con- 
stancy, and that the real cause is as yet unknown 
(Phillip). 



STREPTOCOCCUS. 361 

The theory that scarlet fever is of streptococcus Relation of 
etiology has been held particularly by Babes, scarlet Fever. 
Klein, Moser, Gordan and Baginsky and Sommer- 
feld. Some have held that streptococci isolated 
from the disease show distinctive properties and 
deserve the name of Streptococcus scarlatina. This, 
however, is not agreed to by most bacteriologists, 
the organisms not differing from streptococci ob- 
tained from various sources. The organisms are 
not found constantly in the erythematous eruption. 

Virulent streptococci are found on the tonsils 
almost invariably in scarlet fever. In 65 per cent, 
of the cases a membrane is formed (Ranke), and 
this is often due to the streptococcus, which is 
sometimes, however, associated with diphtheritic 
infection. The frequency with which streptococci 
invade the blood during scarlet fever is related to 
the severity of the disease. Occasionally they are 
found in mild cases, which run a short, uncompli- 
cated course, but "more frequently in severe and 
protracted cases, in which there also may develop 
local complications and clinical signs of general 
infection, such as joint inflammations" (Hek- 
toen). Baginsky and Sommerfeld found strepto- 
cocci in the blood and organs of each of eighty- 
two fatal cases. Hektoen states, however, that 
streptococcemia is not necessarily present in fatal 
cases. 

At the present time there is not sufficient ground 
for considering streptococci as the specific agent 
in scarlet fever, although they are undoubtedly the 
cause of the most frequent and serious complica- 
tions. The mortality of the disease probably is 
greatly raised by mixed infections with the strepto- 
coccus. 



362 



INFECTION AND IMMUNITY. 



Beneficial 
Influences. 



Effect on 
Sarcoma. 



Streptococcus nitrates or cultures may cause de- 
generative changes in the spinal cord (Homen 
and Laitinen). 

Certain strains of streptococci are said to exer- 
cise a curative effect in experimental anthrax. 
Emmerich and di Mattei found that by intra- 
venous injection of the cocci rabbits could be saved 
from an anthrax infection which otherwise would 
prove fatal in forty-eight hours. This result can 
not always be obtained, and it may be that only 
certain strains have this effect (Zagari, cited by 
Lingelsheim). It is noted occasionally that lupus 
improves or actually heals following an attack 
of erysipelas. A reputed effect of a similar nature 
in tuberculosis of the lungs was mentioned above. 

The rather old observation that an attack of 
erysipelas often causes a decrease in the size of 
malignant tumors, especially sarcomas, received 
some confirmation from the experimental work of 
Fehleisen. With the hope of reproducing erysipe- 
las with pure cultures, Fehleisen had inoculated 
streptococci into those suffering from such tumors. 
Among six patients so inoculated, a decrease in the 
size of the tumor was noted in five. Killed cul- 
tures were tried without effect. Coley's mixture 
of killed cultures of the streptococcus and Bacillus 
prodigiosus received rather extensive trial as a 
substitute for living cultures of the streptococcus, 
and in many instances improvement and even 
cures have been reported. Others have had no 
favorable results. Senn used the preparation in 
twelve cases of inoperable sarcoma "with negative 
results." The Bacillus prodigiosus is supposed in 
some way to increase the efficacy of the strepto- 



STREPTOCOCCUS. 363 

coccus toxin; it contains a toxic protein. These 
toxins seem to have no influence on carcinomas. 

Concerning the natural susceptibility and im- immunity and 
munity of man to infections with the streptococcus 
little is known. It seems probable that the un- 
impaired mucous surface resists invasion by the 
organisms which occur constantly in the mouth 
cavity; the physical protection of the intact sur 
face, the rapid desquamation of epithelium, the 
rapid excretion with the saliva, the inhibiting in- 
fluence of the saliva on the proliferation of bac- 
teria and the destruction of bacteria by the leuco- 
cytes which constantly appear on the mucous sur- 
face are probably important factors in this local 
resistance. Congestion of these surfaces, espe- 
cially the tonsils, from any cause, as from ex- 
posure, or the occurrence of some other infection, 
as may be the case in scarlet fever, may lower the 
local protective powers. And, as stated, the serum 
and plasma which exude in simple (?) catarrhal 
conditions or other inflammations, provide a me- 
dium which favors the growth and development of 
virulence by streptococci. 

Concerning the conditions which, in the body, 
antagonize infection, we are largely in the dark. 
It has been impossible to demonstrate antitoxic 
and bactericidal substances in the normal serum 
of man. Streptococci grow freely in fresh normal 
serum which contains no leucocytes. (Weaver and 
G. F. Kuediger.) Phagocytosis of streptococci 
first came under the observation of Metchnikoff, 
who in 1887 noted it as a striking occurrence in 
erysipelas. Only the microphages took up the cocci. 
The marked lucocytosis which is noted clinically 
suggests, but of course does not prove, that the 



364 INFECTION AND IMMUNITY. 

leucocytes take an active part in the destruction 
of the cocci. Experimental work showing such a 
relationship is not lacking, however. Bordet con- 
cluded that all the protection which guinea-pigs 
and rabbits show against streptococci is due to 
the phagocytes. In actual infection streptococci 
have often been found within the leucocytes of the 
blood and inflammatory exudates. (G. F. Eue- 
diger.) Non- virulent or weakly virulent strains 
are phagocytized more readily than the virulent in 
experimental work. Euediger also demonstrated 
conclusively that the streptococci taken up by poly- 
morphonuclear leucocytes may be killed by the lat- 
ter. Hence the evidence in favor of a protective 
role by the leucocytes is more than presumptive. 
Euediger suggests the importance of the leuco- 
cytic toxin of the streptococcus for the develop- 
ment of infection. It may either kill the leuco- 
cytes or cause negative chemotaxis, and under these 
conditions proliferation of the cocci may proceed. 
Acquired The streptococcus usually is classed with those 
organisms, infection with which does not cause the 
development of lasting immunity. A certain 
amount of immunity probably is established, how- 
ever. This -is suggested by the results of Fehlei- 
sen, who could not always cause second attacks 
of erysipelas by the inoculation of pure cultures 
into the susceptible. It is also suggested by the 
ease with which relatively high resistance can be 
produced in animals by brief immunization. A 
streptococcus infection of the horse which occurs 
naturally ("Druse") is said to produce immunity 
which lasts for a year or two. 

One may immunize animals either with toxic 
nitrates or with killed and living cultures. The 



Immunity. 



STREPTOCOCCUS. 



365 



filtrates are much less effective in producing im- immunization 
munity than the bacterial cells, and in the hands 
of many no immunity whatever could be estab- 
lished. 

A number of different principles have been fol- 
lowed in immunizing with cultures. It seems that 
virulent strains cause a higher degree of immunity 
and a serum of higher protective power for other 
animals than strains of low virulence. On this 
account Marniorek, and also Aronson, immunize 
horses with streptococci, the virulence of which has 
been pushed to a very high point by passing them 
through rabbits. Strong resistance is induced by 
this method, and the immune serum, particularly 
that of Aronson, shows distinct protective power 
for other animals. Such serums, however, have 
the highest protective power against the particu- 
lar strain which was used for immunization, al- 
though the serum of Aronson is not devoid of pro- 
tective powers against other pathogenic strains. 
Concerning the serum of Marmorek there are di- 
vergent opinions. In the hands of Marmorek it 
is highly protective in animal experiments; others 
have found it without value. The method of Mar- 
morek and of Aronson rests not only on the basis IffipHcity 
that strains of the highest virulence will give the of streptococci. 
strongest serums, but also on the assumption of 
the unity of all pathogenic streptococci. If all 
are alike in their biologic and pathogenic proper- 
ties, a serum which protects against one should 
protect against all. As pointed out, there is at 
present not sufficient ground for considering the 
streptococci of erysipelas, scarlet fever, rheuma- 
tism, sepsis, etc., as independent species. By cul- 
tivation and passage it is possible to so modify any 



366 INFECTION AND IMMUNITY. 

one of them that it is indistinguishable from the 
others, on the basis of morphology and patho- 
genicity. On the other hand they are not all 
identical in some very important properties. For 
example, not all strains produce hemolysin to the 
same degree, and they differ greatly in their sus- 
ceptibility to the action of an agglutinating serum. 
We have also to remember that pathogenicity for 
animals is not a reliable index of pathogenicity for 
man. From these confusing conditions we can 
only regard the question of unity or multiplicity 
of streptococci as an open one, which may be de- 
cided by future investigations. 
Univalent and The serums of Marmorek and Aronson are uni- 
Serums. valent serums, a single strain being used for im- 
munization. Certain investigators, believing in 
the multiplicity of streptococci, utilize several 
strains in immunization. The serum of Denys is 
obtained by immunizing with several strains the 
virulence of which has been artificially increased. 
Such a serum would, theoretically, have a wider 
range of action than a univalent serum ; it is poly- 
valent. Having in mind the fact that passing a cul- 
ture through rabbits increases the virulence of 
the organism for the rabbit, but alters its virulence 
for the original host (man), Tavel, Moser and 
Menzer prepare serums on a different basis. 
Tavel employs several strains of streptococci cul- 
tivated from pathological processes in man, avoid- 
ing such alterations in virulence as would be caused 
by passing the cultures through animals. On the 
assumption that scarlet fever is a streptococcus 
disease, Moser immunizes horses with strains 
(about twenty) which are cultivated from cases 
of scarlet fever. In a similar manner, Menzer, 



STREPTOCOCCUS. 



36i 



supposing that rheumatic fever is a streptococcus 
infection, immunizes with a number of strains cul- 
tivated from the tonsils of cases of rheumatism. 
Both Moser and Menzer avoid passage in order to 
retain the original biologic properties of the cul- 
tures. 

In animal experiments, some of these serums, 
and particularly that of Aronson, have exhibited 
strong protective powers. Aronson's serum in 
doses of 0.0004 to 0.0005 c.c. protects a mouse 
against ten fatal doses of the streptococcus given 
twenty-four hours later than the serum. A serum 
of which 0.01 c.c. protects against a dose known 
to be fatal is considered of normal strength. The 
present serum, then, is of twenty- to twenty-five- 
fold value. In some instances animals can be 
saved when the serum is used some hours after 
infection, but this period is a brief one. 

Statements concerning the value of antistrepto- 
coccus serums in treating human infections are 
very conflicting. The serum of Marmorek has 
been given more general trial than any other, and 
the results have not been satisfactory. Favorable 
effects, such as the lowering of temperature and 
improvement in the general condition, have been 
reported, but the serum possesses no distinct cura- 
tive power in established infections. Koch and 
Petruschky deny that it has a prophylactic power 
in experimental erysipelas. Escherich, by using 
the serum of Moser, and Baginsky, by using that 
of Aronson, observed a shortening of the course, 
a reduction of the fever and general improvement 
in cases of scarlet fever. Moser claims that it re- 
duces the mortality of the disease. The use of 
anti streptococcus serum in the treatment of scarlet 



Serum 
Protection. 



Serum 
Therapy. 



Scarlet 
Fever. 



368 



INFECTION AND IMMUNITY. 



fever does not commit one to the streptococcus 
etiology of the disease, but rather to the impor- 
tance of streptococcus complications; hence, if the 
danger of these complications can be reduced by 
antistreptococcus serum its use is justified. It 
remains for future work to demonstrate to our 
satisfaction that it has such value. 

What has been said concerning the treatment of 
Rheumatism, scarlet fever with the serums of Moser and Aron- 
son also applies to the treatment of rheumatism 
with the serum of Menzer. Favorable reports have 
appeared concerning its value, but a sufficient mass 
of experience has not accumulated to permit of 
satisfactory judgment. "So much appears from 
observations in man that the different streptococcus 
serums are harmless" (Dieudonne). 

As nearly as can be learned at present, anti- 
Properties streptococcus serum is protective (and cura- 
tive ( ?) ) because of its ability to stimulate phago- 
cytosis, rather than because of serum antitoxins 
or bacteriolysins. This was indicated by the ob- 
servations of Bordet in animal experiments, in 
which marked phagocytosis of streptococci took 
place in the peritoneal cavity of immunized ani- 
mals, but very little in normal animals. A simi- 
lar condition was noted in the test-glass experi- 
ments of Denys and van der Yelde. A mixture 
of normal rabbit serum and leucocytes showed 
very little phagocytosis of streptococci, whereas 
the addition of antistreptococcus serum caused 
active phagocytosis, with death of the cocci. The 
presence of a definite substance in the serum which 
stimulated phagocytosis was conceived by van der 
Velde and also by Lingelsheim. It was heat-re- 
sistant (62° to 65° C), and was not destroyed 



Stimulation of 
Phagocytosis. 



STREPTOCOCCUS. 369 

by dilute acids and alkalies (cited byLingelsheim). 
Hence its resistance is greater than the opsonins 
of Wright and Douglass, but perhaps not greater 
than the bacteriotropic substances of Neufeld. It 
is probable that some of these substances are heat- 
resistant and others heat-susceptible. 

The agglutinability of streptococci from differ- Agglutination. 
ent sources, and even from the same source, varies 
a great deal. Also the normal serums of man and 
animals have a variable agglutinating power for 
different strains of streptococci. By immunization 
with a given strain the agglutinating power is in- 
creased, but not uniformly for all strains. Com- 
monly the strain used for immunization is agglu- 
tinated more strongly than heterologous strains, 
the latter sometimes undergoing no agglutination 
whatever. These variations do not depend on dis- 
coverable differences in the cocci or the diseases 
which they produce. A given antistreptococcus 
serum does not agglutinate equally all streptococci 
from cases of scarlet fever (Weaver). Also strep- 
tococci vary greatly in their ability to stimulate 
to the formation of agglutinins. On the whole 
those which produce long chains are more suscep- 
tible to agglutination and yield stronger serums 
than those with short chains. (Aronson, Tavel, 
v. Lingelsheim. ) By passage the agglutinating 
properties undergo rather complex changes. The 
organism then produces a stronger agglutinating 
serum and is agglutinated more readily by this 
serum than the same strain which had not been 
passed through animals. If passage is discon- 
tinued it reverts to its former condition. 

The variations are such that the agglutination 



370 INFECTION AND IMMUNITY. 

reaction is of little or no value in differentiating 
different types of streptococci. 

As to the clinical value of the test for the diag- 
nosis of scarlet fever, the conclusions of Weaver 
may be cited : 

1. Of streptococci cultivated from cases of scar- 
latina, some are agglutinated by almost all scar- 
latinal sera, but at dilutions varying from 1/60 
to 1/4000; others are agglutinated by the same 
sera with less constancy and at lower dilutions, and 
many are not agglutinated at all. 

2. Streptococci cultivated from cases of scar- 
latina are agglutinated by sera from cases of lobar 
pneumonia and erysipelas at about the same dilu- 
tions as by scarlatinal sera, and in the case of ery- 
sipelas even at higher dilutions. 

3. The same appears to be true of typhoid fever 
serum, so far as limited tests indicate, and to al- 
most the same extent of puerperal-fever serum. 

4. The agglutination reaction between the 
streptococci cultivated from cases of scarlatina and 
the serum from cases of scarlet fever is in no way 
specific, and can not be of any value as a means of 
diagnosis. 

By growing streptococci on a medium which 
contains serum (serum bouillon), the}' form fewer 
and shorter 'chains and are better suited for ag- 
glutination tests. 

III. STAPHYLOCOCCI. 

Staphylococci are spherical cells from 0.7 to 0.9 
microns in diameter, typically, and by light stain- 
ing are often seen to consist of two hemispheres, 
which are separated by a delicate cleft. In pus 
.they are found in small groups of two to nine or 



STAPHYLOCOCCUS. 



371 



ten, ocasionally as diploeocei, tetrads or very short 
chains. 

They are luxuriant growers on nearly all media Cultivation and 
which are suitable for bacteria, preferring, how- erties. 
ever, a slightly alkaline reaction. Growth is best 
in the presence of oxygen, but proliferation occurs 
in its absence. Sputum, serum and ascitic fluid 
are favorable media, and in the last two the cocci 
may be agglutinated. An alkaline reaction is pro- 
duced in litmus milk, and the casein is precipitated 
and partly digested. The production of a proteo- 
lytic ferment is shown by liquefaction of gelatin 
and the formation of a clear zone about the colo- Ferments. 
nies when grown in plates which contain coagulat- 
ed serum (Loeb, cited by Neisser and Lipstein). 
Albumen is changed into peptone. Loeb distin- 
guishes between a ferment which liquefies gelatin 
(gelatinase, a "collolytic" ferment), and one which 
digests albumen (tryptic ferment). Gelatinase is 
present in staphylococcus filtrates and normal 
serums are rich in antibodies for it. A fat-splitting 
ferment (lab ferment) is also present in the 
filtrates. The fact that the pus which is produced 
in staphylococcus infection does not coagulate may 
be due to the action of the proteolytic ferment, 
which digests the fibrinogen. 

Van der Velde had noted in 1894 that "staphy- staphyioiysin. 
lotoxin" (staphylococcus filtrates) cause hemoly- 
sis. Xeisser and Wechsberg, in 1901, by growing 
the organisms in bouillon of suitable alkalinity, 
obtained hemolytic filtrates, giving the name of 
staphyioiysin to the hemolytic principle. The hemo- 
lytic action of the staphylococcus is readily seen 
in cultures on blood-agar plates; a zone of hemo- 
lysis forms about the colonies. Erythrocytes of the 



372 INFECTION AND IMMUNITY. 

rabbit, when placed in bouillon cultures, undergo 
hemolysis. Staphylotoxin also produces hemolysis 
in the living body. The maximum production of 
staphylolysin occurs after a growth of nine to 
fourteen days in alkaline bouillon, and nearly 
all pathogenic strains yield it, whether aureus, 
albus or citreus. It is not formed by non-patho- 
genic strains. The toxin is destroyed by exposure 
to a temperature of 56° C. for twenty minutes. A 
specific antitoxin is present in many normal 
serums and may be increased by immunization 
with the toxin or the living organisms. 
Leucocidin. In 1894 van der Velde found in the pleural 
exudates caused by inoculation with killed cultures 
of the staphylococcus a substance which is toxic 
for leucocytes, causing them to swell and the nuclei 
to disappear. This substance is called leucocidin. 
It is also produced in culture media, but the ability 
to form it is not so widely distributed as in the 
case of the hemolysin. Leucocidin is a true toxin, 
like the hemolysin; most normal serums contain 
antileucocidin, and the latter is increased by im- 
munization with the toxin.* The suggestion 
is a natural one that leucocidin may be a factor in 
combating phagocytosis in infections with the 
staphylococcus. Neisser and Wechsberg' de- 
vised a "bioscopic method 7 '' of determining the 
cytocidal action of the toxin. Living leucocytes, 
like other living cells, have the power of decoloriz- 
ing methylene blue when oxygen is excluded. The 
destructive action of the toxin on the leucocytes 
is indicated by the failure of this reduction when 
the toxin is mixed with the cells. 

* Leucocidin and staphylolysin will not yield antitoxins 
when their activity has heen destroyed by heat. 



STAPHYLOCOCCUS. 



373 



Old culture nitrates (two to three weeks) show Toxic 
a rather high degree of toxicity for animals, pro- 
ducing extensive degeneration of the convoluted 
tubules in the kidney, a degeneration which is 
somewhat selective; hemorrhages into the in- 
testinal mucosa; degeneration of the ganglionic 
cells, and fever. According to Levaditi, a mast- 
cell leucoc} r tosis develops. The nature of the fever- 
producing substance is unknown. The toxicity of 
nitrates is said to be destroved by a temperature 
of 56° C. 

Cultures of the staphylococcus killed by heat Endotoxin ?> 
show little toxicity, hence the question of the ex- 
istence of an endotoxin is on no better basis than 
in relation to the streptococcus. It is possible that 
the heat required to kill the organisms destroys the 
endotoxin as well as the soluble toxins mentioned 
above. The virulence of the organisms has no 
direct relationship to the hemolysin or leucocidin, 
or the toxicity of the filtrates. Very pathogenic 
strains may produce a nitrate of little or no 
toxicity. It seems then that the essential patho- 
genic agent of the organism is unknown; as in 
the case of the streptococcus, its infectiousness may 
depend on its ability to resist the antibacterial ac- 
tivities of the body (phagocytosis, bacterioly- 
sis (?) ), which, of course, is a very indefinite 
assumption. What part the leucocidin plays in 
this resistance is not definitely known. 

The many varieties of the staphylococcus are varieties of 
differentiated on the basis of pathogenicity, pig- coc?uI.°" 
ment formation, liquefaction or non-liquef action 
of gelatin, and other cultural properties. The 
albus differs from the aureus only in its inability 
to form pigment, and it can qoI be made to in- 
quire this property. Pigmenl is formed most 



374 INFECTION AND IMMUNITY. 

abundantly on potato, whereas little is formed 
on blood serum. Other pigment-forming varieties 
are : 8. cereus flavus, 8. pyogenes citreus, 8. scar- 
latinus and Micrococcus hematodes. The 8. epi- 
dermidis alous of Welch is of low virulence. Weich- 
selbaum obtained a 8. endocardititis rugatus from 
a case of endocarditis. Not all of these varieties 
produce soluble toxins. The pigment of 8. aureus 
is an excretion product which is formed only in 
the presence of oxygen. It is insoluble in water, 
soluble in alcohol and ether, and gives the reac- 
tion of a lipochrome (i. e., the pigment may be 
saponified and gives the lipocyanin reaction in 
which the pigment turns blue when treated with 
concentrated sulphuric acid). 
Resistance Aside from wide individual variations, the re- 
sistance of staphylococci to heat depends on the 
concentration of the suspension, the nature of the 
medium (whether water, gelatin or pus), and 
whether the test is a dry or wet one (Neisser and 
Lipstein). Eighty degrees centigrade for one-half 
to one hour kills them under all conditions, and 
60° C. for one-half hour kills many strains when 
suspended in bouillon. They are not killed by re- 
peated freezing and thawing, and are very resist- 
ant to desiccation. When in the form of fine dust 
they die in twenty-eight days (Ivirstein). Eesist- 
ance to the action of sunlight is variable; some 
strains are killed in from three to five hours. 

Staphylococci have fairly high resistance to anti- 
septics; when dried, corrosive sublimate (1/1000) 
kills them in two to three hours, and when im- 
bedded in pus thirteen to sixteen hours are re- 
quired (Ottaviano). Methyl alcohol, tincture of 
green soap and methyl violet are relatively good 
disinfectants. Methyl violet in a dilution of 



STAPHYLOCOCCUS. 



375 



1/10,000 kills them in five to fifteen minutes 
(Stilling). Formalin readily hinders develop- 
ment, but its bactericidal power is low. It is 
difficult or impossible to sterilize wounds infected 
with the staphylococcus by means of antiseptics. 

Staphylococci are very widely distributed in na- 
ture and are to be found constantly in the super- 
ficial layers of the epidermis (S. epidermidis al- 
ius) . 

In infections the staphylococcus attracts large Leucotactic and 
numbers of leucocytes, and the pus does not coagu- substances. 
late. The substance which attracts leucocytes is 
heat-resistant, since killed cultures will cause 
abscesses. In all but the most superficial lesions 
a characteristic result of infection is that of cell 
necrosis and the liquefaction of tissues. Neisser 
and Lipstein state that the necrotizing substance 
is a soluble toxin, since culture filtrates cause 
marked necrosis of the internal organs when in- 
jected (liver, heart, kidney). "Hence in staphylo- 
mycosis we can distinguish two active substances 
(von Lingelsheim), the leucotactic substance in 
the bodies of the cocci and the more important 
soluble staphylotoxin which exercises not only 
a local but also a general toxic action on the body*' 
( Xeisser and Lipstein). 

Davidson produced amyloid degeneration in 
rabbits and mice by the injection of living cultures. 
Tli is was confirmed by Lubarsch, who found the 
condition most readily produced in the chicken 
and with more difficulty in the mouse, rabbit and 
dog. It rarely results if suppuration is avoided. 
Killed cultures may be used. 

Rabbits and mice are the most susceptible ani- 
mals. The susceptibility of man is much greater. 



Amyloid 
Degeneration. 



376 INFECTION AND IMMUNITY. 

susceptibility The organisms are most virulent for rabbits when 
injected intravenously, and a variety of lesions 
may result, as abscesses in various parts of the 
body (especially the kidney, heart and muscles), 
arthritis, endocarditis, etc. They are less patho- 
genic when injected into the pleural or peritoneal 
cavities. Eabbits are rarely to be infected by the 
feeding of cultures. In experimental infections 
degenerations of the axis cylinders in the white 
and gray matter, and of ganglionic cells, have been 
noted. The virulence of staphylococci is subject 
to great variations, and it may be increased by 
passage. In passing a culture through the rabbit 
eight times, Lingelsheim reduced the fatal dose 
for rabbits from 5 c.c. to 1/100 c.c, but a corre- 
sponding increase in virulence for the mouse and 
guinea-pig did not occur. Virulence for animals 
is not a reliable index of virulence for man. 
infections The staphylococcus is the most common pus 
producer in man. The most frequent infections 
are those of the skin, the organisms gaining en- 
trance through the hair follicles rather than 
through the sweat ducts (Unna), resulting in such 
conditions as acne pustules, abscess of the skin 
and subcutaneous tissue, furuncles and carbun- 
skin - cles. They are found almost constantly in the 
lesions of impetigo and often in pure culture. 
They have been much vaunted as a cause of 
eczema and they may be important as a secondary 
agent in this condition. The ordinary eczema prob- 
ably is not parasitic in its cause, however (Sabou- 
raud), and Neisser and Lipstein dispute the claim 
of Bender and -others that eczema produced by 
staphylococcus filtrates is due to products of the 
microbe. This conclusion was justified, since the 



STAPHYLOCOCCUS. 



377 



Mucous 
Surfaces. 



same results were obtained with pure bouillon of 
similar alkalinity, the property could not be de- 
stroyed by heat, and antistaplryloeoccus serum was 
not able to prevent the dermatitis. Furuncles may 
be produced by rubbing virulent cultures into the 
skin, and abscesses by the injection of minute 
amounts. The staphylococcus causes purulent or 
seropurulent conjunctivitis rather infrequently. 
Primary infections of cavities which communicate 
with the surface, as the antrum of Highmore, the 
middle ear, nose, bronchi, lungs and tuberculous 
cavities, are not uncommon, and mixed infections 
with the staphylococcus in these localities is the 
rule, regardless of the primary cause. Infection 
of the mucous surfaces is less common than of the 
skin, however. It rarely causes aphthous inflam- 
mations, anginas, pneumonia, enteritis and cys- 
titis when unmixed with other organisms. 

Staphylococcus septicemia of great virulence oc- Septicemia. 
casionally follows primary infection in other parts 
of the body, as wound infections, tonsillitis, puer- 
peral infection (rare) and the so-called malignant 
carbuncles of the upper lip. In such instances a 
thrombophlebitis may be the means by which the 
organisms are poured into the circulation in large 
numbers. Inflammations of the serous surfaces, |JJJ"® es 
as the pleura, peritoneum and endocardium, are and Bones. 
rarely primary, but follow systemic infection ; the 
endocarditis usually is ulcerative and leads to 
metastatic foci of infection. Staphylococci have a 
particular affinity for the bony tissues, especially 
the bone marrow and the periosteum ; they are the 
most common agent in the production of osteomye- 
litis and cause the so-called periostitis albuminosa. 
It is thought that they may persist in bone lesions 



378 



INFECTION AND IMMUNITY. 



Mixed 
Infections. 



Leucocytes 
in Natural 
Immunity. 



Bactericidal 
Action of Leu- 
cocytes and 
Leucocytic 
Exudates. 



for a period of years and later start up a fresh 
process. They involve the joints less frequently, 
but have been found, presumably as secondary 
agents, in acute rheumatism, and as the primary 
cause in pyemic abscesses of the joints. They are 
found occasionally in abscesses of the mammary 
and parotid glands, liver, lungs, and in pyorrhea 
alveolaris (rare) . The cultivation of staphylococci 
in. a pure state from the tissues does not of neces- 
sity indicate that they are the essential organism 
in the process (smallpox, rheumatism, etc.). Pre- 
vious infections by many organisms, and likewise 
traumas, predispose to localization of the staphy- 
lococcus, and any infectious process in the skin is 
likely to be invaded by these organisms secondarily. 

Infections with the staphylococcus are charac- 
terized by both local and general leucocytosis, the 
local leucocytosis being a part of the suppurative 
process. As stated above, the staphylococcus con- 
tains a thermostabile constituent, which exerts a 
positive chemotatic effect on the leucocytes. Al- 
though it is possible to consider the accumulation 
of the leucocytes merely as the expression of this 
affinity, it has been shown with sufficient clearness 
that polymorphonuclear leucocytes are able to in- 
gest living staphylococci and kill them.* They 
may be found within the leucocytes in both natural 
and experimental infections. When injected into 
the pleural or peritoneal cavity of the guinea-pig 
phagocytosis is well begun within one-half hour 
and reaches its height in four to five hours. 

Experiments which were begun by van der Velde 
in 1894 demonstrate the bactericidal action of leu- 

* Phagocytosis of staphylococci was first observed by 
Kirch in 1889. 



STAPHYLOCOCCUS. 379 

cocytic exudates. The action is not so strong in 
the cell-free exudate as when the leucocytes are 
present, and when the leucocytes are caused to dis- 
integrate by some means, as by alternate freezing 
and thawing, trituration, the action of leucocidin, 
or treatment with distilled water, the bactericidal 
power of the fluid is increased. Presumably the 
leucocytes discharge their bactericidal contents into 
the surrounding fluid as a result of such inju- 
ries. The nature of the bactericidal substance is 
not known exactly; from the fact, however, that 
leucocytes contain complement it has been suggest- 
ed that they discharge this complement which then 
acts with amboceptors in the serum in destroying 
the organisms. It is possible that the cocci before 
they are taken up by the leucocytes have absorbed 
amboceptors and after their ingestion are suscepti- 
ble to the action of the endocellular complement. 
In contrast to the distinct bactericidal power of the 
leucocytes stands the very low or entire absence of 
a similar action by both normal and immune 
serums. It would seem, then, that the most power- 
ful agency in natural resistance to invasion by the 
staphylococcus is represented in the phagocytic 
and bactericidal activities of the leucocytes. Opso- 
nins are essential for phagocytosis. 

In 1888 Richet and Hericourt showed that it Active 
was possible to increase the resistance of the rabbit 
against the staphylococcus by immunization with 
pure cultures.* 

One may immunize either with living or killed 
cultures or with culture filtrates. Immunization 

* Their experiments in protecting and curing other ani- 
mals with antistaphylococcus serum represent the first at- 
tempt made in the direction of passive Immunization. 



380 INFECTION AND IMMUNITY. 

with the bacterial cells must proceed slowly in 
order to avoid killing the animals. When filtrates 
containing leucocidin or staphylolysin (hemolysin) 
are used, antitoxins for these substances are 
formed. The antistaphylolysin obtained for one 
strain neutralizes the hemolysin of all strains. 
The most prolonged immunization with bacterial 
cells causes no appreciable increase in bacterioly- 
sins. 

Protection The serum of one who has recovered from a 
Serums, staphylococcus infection, or that of immunized an- 
imals, is protective for other animals; 0.1 to 0.2 
c.c. of an immune serum given subcutaneously 
protected mice from a fatal dose of cocci given 
two hours later, whereas other mice were killed in 
from 8 to 12 hours. When the serum was given 
24 hours in advance of the culture, 0.02 to 0.03 
c.c. saved them (v. Lingelsheim, cited by Neisser). 
The results of Petersen and of Proscher were simi- 
lar. In spite of this rather strong protective ac- 
tion, immune serums have little or no curative 
power. 

Properties ]$ clearer explanation of the action of the im- 

of Serums. 1 

mune serum is given than that afforded by the 
experiments of Proscher, who injected guinea- 
pigs, rabbits and mice with normal and immune 
serums and followed this 24 hours later with in- 
oculation of the cocci into the peritoneal cavity. 
Thirty minutes after injection of the cocci the 
exudate in all animals showed an enormous leuco- 
cytosis. At first they were chiefly mononuclears, 
but later gave place to polvnuclears. In the ani- 
mals which had received the immune serum, mas- 
sive phagocytosis had occurred, and in the course 
of an hour very few cocci were extracellular. On 



STAPHYLOCOCCUS. 381 

the other hand, practically no phagocytosis had 
taken place in the animals which had received the 
normal serum (cited by Neisser). Virulent 
staphylococci were taken up less readily than 
avirulent. Such results suggest that the protective 
power of the serum is due to its ability to stimulate 
phagocytosis, and this in turn depends on the 
increased quantity of bacteriotropic substances 
formed in the serum as the result of immunization 
(Wright and others). 

In the hands of Wright, vaccination with killed Vaccination. 
cultures of the staphylococcus has been very suc- 
cessful in the cure of obstinate cases of acne, fur- 
unculosis and sycosis barbae. Bouillon cultures 
are grown for three weeks and then killed by ex- 
posure to a temperature of 60° C. for an hour. In 
order to control dosage, the vaccine is standardized 
by estimating the number of bacilli in each cubic 
centimeter. This is done by mixing equal quanti- 
ties of the vaccine with normal blood, and, after 
staining a preparation on a slide, determining the 
ratio of cocci to erythrocytes. There being about 
5,000,000 erythrocytes to the cubic millimeter in 
normal blood, the number of cocci is readily reck- 
oned from the ratio which was found. From 
2,500 millions to 7,500 millions of cocci may be 
given in an injection. The quantity to be used is 
determined by the effect which an injection has on 
the opsonic content of the patient's serum. If a 
suitable dose has been given, there occurs a short 
negative phase in which the opsonins are decreased 
in quantity, and this is followed by a rather pro- 
longed positive phase when they undergo an in- 
crease. If too large a dose is given, the negative 
phase is exaggerated and prolonged. In many in- 



382 INFECTION AND IMMUNITY. 

"opsonic stances it has been noted that improvement and 
recovery go hand in hand with an increase in the 
opsonins. The quantity of opsonins present in a 
serum is expressed by an "opsonic index."* 
Agglutination. ^he normal serums of man and many animals 
may agglutinate the staphylococcus, but with no 
constancy. In one instance human serum ag- 
glutinated in a dilution of 1-100 (Kraus and 
Low), and normal goat serum in a dilution of 
1-50 to 1-400 (Amberger, cited by Neisser). The 
serums from cases of staphylococcus infection 
(e. g., osteomyelitis) and of highly immunized an- 
imals undergo an increase in the quantity of ag- 
glutinins. The agglutination usually is strongest 
for the homologous strain, and if other strains are 
agglutinated equally it signifies a close relation- 
ship to the homologous strain. 

From the fact that only pathogenic strains pro- 
duce hemolysin and leucocidin, Neisser and 

* To obtain the opsonic index human leucocytes, ob- 
tained from deflbrinated blood, are washed free of serum. 
and equal parts are added to two equal portions of an emul- 
sion of the staphylococcus. One portion of the emulsion has 
previously been treated with the serum of the patient for 
about twenty minutes, and the other portion with normal 
human serum. The opsonins of the two serums combine 
with the cocci, rendering them susceptible to phagocytosis 
(sensitization). After the leucocytes have been in contact 
with the sensitized cocci for fifteen to thirty minutes, films 
of the two mixtures are stained with the Romanowsky or 
a similar stain, which colors both the cells and the cocci. 
The average number of cocci in say fifty leucocytes on each 
slide is determined. The average phagocytosis in the pa- 
tient's serum divided by that in the normal serum gives the 
opsonic index. For example, if the former showed an 
average of 10 cocci to each leucocyte and the latter an 
average of 5, the index is 2. The degree to which the op- 
sonic index can be raised by the immunization varies. In 
one instance it was increased from .8 to 2.6 ; in another case 
which reacted less vigorously it was raised from .87 to .95. 



MICROCOCCUS CATARRHALIS. 383 

Wechsberg considered them specifically different 
from non-pathogenic strains. This view is borne 
out by the results obtained with the agglutination 
test. Serums obtained by immunization with 
pathogenic strains have a much higher aggluti- 
nating power for these strains than for non-patho- 
genic varieties, and the converse is also true. There 
are, however, many variations in the agglutinabil- 
ity of the members in each group, a fact which in- 
dicates variations in the receptor complex of the 
different strains. It has been suggested that a 
polyvalent serum obtained by immunization with 
a sufficient variety of pathogenic strains will be 
efficient in differentiating the latter from non- 
pathogenic varieties by means of the agglutina- 
tion test. 

Wright, noting an increase in the agglutinating 
power when patients are treated by his method, 
considers that this increase is an index of the im- 
munity which is established. 

IV. MICROCOCCUS CATARRHALIS. 

For some years diplococci resembling the gono- 
coccus and the meningococcus morphologically and 
in staining reactions have been found in the spu- 
tum by a number of observers, and to this coccus 
Pfeiffer gave the name of Micrococcus catarrhalis. 
It is frequently found in the respiratory passages 
in influenza-like infections and other inflamma- 
tory conditions, and occasionally in lobular pneu- 
monia. It may be associated with the influenza 
bacillus or the pneumococcus. Among 140 cases 
of diseases of the respiratory passages Gohn and H. 
Pfeiffer found it eighty-one times, and M. Neisser 
demonstrated it in sixteen cases of whooping- 



The 
Gonococcus. 



384 INFECTION AND IMMUNITY. 

cough, in one of measles and scarlet fever, and in 
two of diphtheria. It loses significance in relation 
to these diseases, however, since Jiindell found it 
frequently in the mucus of the normal trachea, 
and Weichselbaum cultivated it frequently from 
the healthy nasal fossae. According to G-ohn, 
Pfeiffer and Sederl, "The Micrococcus catarrhalis, 
without the association of other microbes, is able 
to cause bronchitis and pneumonia with the clini- 
cal type of pneumonia due to the pneumococcus. 
The symptoms caused by the Micrococcus catarrh- 
alis do not form a clinical type. They resemble 
infections by the pneumococcus or the bacillus of 
Pfeiffer (Influenza)" (cited by Bezancon and de 
Jong). Others are not so positive concerning the 
pathogenic properties of the organism. Its etio- 
logic role is not yet well established. It has little 
pathogenicity for animals, although peritoneal and 
pleural infection is possible in guinea-pigs. 

It differs from the gonococcus and meningococ- 
cus in certain cultural characters. 

V. GONORRHEA AND OTHER INFECTIONS WITH THE 
GONOCOCCUS. 

A. Neisser discovered the gonococcus in 1879, 
cultivated it in 1884, and demonstrated its specific 
relation to gonorrhea by the inoculation of pure 
cultures into the human urethra. It is a diplo- 
coccus, young pairs having a figure-of-eight con- 
tour, whereas older pairs show a typical biscuit 
or coffee-bean shape. The organism is non-motile, 
has no flagella and forms no spores. It can be 
cultivated only on media which contain serum, 
ascitic or a similar fluid. Its failure to stain by 
Gram's method is of great diagnostic importance 



GOXOCOCCUS. 



385 



in the examination of urethral discharges; other 
organisms resembling the gonococcus are found in 
the urethra and vagina with great rarity. The 
reaction loses its differential value in the examina- 
tion of secretions of the nose, mouth, and, to some 
extent, of the conjunctiva, where the meningococ- 
cus and the Micrococcus catarvhalis may be en- 
countered. 

In the purulent stage of a gonorrheal infection phagocytosis. 
the cocci are found almost entirely within the leu- 
cocytes, whereas in earlier stages, when the dis- 
charge is slight and of a mucous character, and 
also during convalescence, when the secretion 
again becomes mucous, they are largely extracel- 
lular. They are never within the nuclei. The 
process is one of active phagocytosis in which the 
cocci play a passive role. They occur not only on 
the surface of the epithelium, but penetrate be- 
tween and beneath the epithelial cells, and even 
into the adjacent connective tissue. 

In culture media growth is slow and scant, and cultivation 
cultures rarely live longer than one or two weeks, 
unless they are transplanted to suitable fresh media. 
On the latter they may be carried through many 
generations without losing their virulence. When 
dried they die very quickly, but may live for some 
hours on linen (towels) or the skin, and for 
twenty-four hours in warm water. They are very 
susceptible to temperatures above 42° to 43° C. 
and show very little resistance to antiseptics, par- 
ticularly the silver salts. 

The gonococcus secretes no soluble toxin, but fexfcityfMd 
contains an endotoxin or toxic "protein" which v,ru,ence - 
causes local and general symptoms in both man 
and animals. Dead cultures produce an inflamma- 



Susceptible 



386 INFECTION AXD IMMUNITY. 

tory exudate in the peritoneal cavity of guinea- 
pigs and mice, resulting in death if the dose is 
sufficiently large, and when injected into the 
urethra of man a temporary inflammation results. 
An actual infection of any sort can not be pro- 
duced in animals; the cocci are killed without be- 
ing permitted to proliferate. The endotoxin (gon- 
otoxin) is fairly resistant to heat, being destroyed 
only after prolonged exposure to a temperature of 
100° C. 

In man the mucous membranes and endothelial 
Tissues, surfaces are more susceptible to infection than 
other tissues. The urethra of male and female at 
all ages, the conjunctiva in the new-born, the 
vagina, uterus and tubes are probably, the most 
susceptible. Less susceptible are the vagina in 
older women, especially those who have borne chil- 
dren; the bladder, and in adults the conjunctiva. 
It is remarkable that there are so few cases of 
gonorrheal ophthalmia in adults, considering the 
opportunities for infection. Infection of the 
mouth, nose and tear sacs is extremely rare. Ex- 
tension from the urethra to adjacent structures 
takes place either by way of the surfaces, as in 
involvement of the prostate, epididymis, glands of 
Bartholin, uterus, tubes, ovaries, peritoneum, blad- 
der and kidneys, or by way of the lymphatics as in 
infections of the periurethral tissue or cellular tis- 
sue of the pelvis. Usually infections of the bladder 
and kidney, and not infrequently of the prostate. 
Fallopian tubes and pelvic tissue are of a mixed 
character (staphylococcus, streptococcus), but not 
necessarily so. Arthritis, tendovaginitis, endocar- 
ditis, which usually is vegetative but may be ulcer- 
ative, are the more common metastatic complica- 



GOXOCOCCUS. 387 

tions. Less frequent are pericarditis, pleuritis, 
subcutaneous abscesses and iritis. As to whether 
the cutaneous phenomena sometimes seen are due 
to metastases or are of purely toxic origin seems to 
be undetermined. The blood stream ma}' be in- 
fected by way of the lymphatics or local blood 
vessels (gonorrheal thrombosis). 

The influence of the enormous phagocytosis of 
the cocci on the course of gonorrhea is unknown. 
Since the ingested cocci usually have a typical 
form and stain well, it would seem that they resist 
the action of the leucocytic ferments. Likewise 
the nuclei of the leucocytes usually stain well, 
hence there is no evidence of a marked toxicity 
of the cocci for these cells. The mechanical im- 
prisonment of the organisms by the leucocytes 
may be of influence in localizing the infection. 

During the course of gonorrhea "there takes Urethral 
place a pronounced metaplasia of the epithelium 
in which the cylindrical cells are changed into a 
more cuboidal and even pavement form." Follow- 
ing this change the gonococci are limited to the 
surface of the altered epithelium and penetrate 
more deeply only in the vicinity of the glands and 
crypts. "Eventually the gonorrheal process is 
limited to such isolated points and the gonorrhea 
thereby enters into a chronic stage" (observations 
of Finger, cited by Neisser and Scholtz). 

The conditions which cause the subsidence of chronic 
acute gonorrhea and allow it to persist as a chronic 
infection have been the subject of much specula- 
tion, unproductive for the most part. It is not 
due to a decrease in the virulence of the cocci 
since their original infectiousness is retained for 
others; nor does the local resistance of the mucous 



388 IXFECTIOX AXD IMMUNITY. 

membrane reach a high point, since reinfection, 
or better "superinfection" is possible at any time. 
A man suffering from chronic gonorrhea and 
having infected his wife, may again be infected 
by his wife when the gonorrhea of the latter has 
become subacute or chronic. It has been suggested 
that the condition in chronic gonorrhea may be 
one of "mutual habituation between the mucous 
membrane and the gonococcus," i. e., a habituation 
between this particular mucous membrane and 
this particular gonococcus. Because of prolonged 
existence under unvarying conditions, the growth 
energy of the organism may have become less, 
whereas, if it is placed in a slightly different me- 
dium (transference to another individual), its 
growth energy (ability to proliferate), becomes 
augmented, and reinfection of the original host 
with the same strain becomes possible. 

It has often been noted that subsequent attacks 
run a milder course than the primary infection, 
but susceptibility is always present. 
immunity. Mendez, Calvino, and also de Christmas have 
immunized with the coccus or toxic substances 
prepared from it. By growing the organism in 
serum bouillon de Christmas prepared a toxin, 
the toxicity of which was tested by intracerebral 
injections in the guinea-pig. Immunization of 
the guinea-pig resulted in a serum with antitoxic 
properties. Corroborative work has not been pub- 
lished. 



VI. EPIDEMIC CEREBROSPINAL MENINGITIS. 

M cau*mg Acute inflammation of the meninges may be 
Meningitis, caused by a number of micro-organisms: Micro- 
coccus meningitidis, also called the Diplococcus 



MENINGOCOCCUS. 389 

intracellularis meningitidis, or briefly the men- 
ingococcus; Diplococcus pneumonuB; y Streptococ- 
cus pyogenes; Staphylococcus pyogenes; Bacillus 
influenza; Bacillus pneumonia' ; Bacillus typho- 
sus; Bacillus coli communis; Bacillus mallei; Ba- 
cillus pestis. The first two of this number, the 
meningococcus and the pneumococcus, in addition 
to causing sporadic cases, also produce more or 
less extensive epidemics of so-called primary men- 
ingitis. That the pneumococcus may also cause 
meningitis secondary to pneumococcus infections 
in other parts of the body has been mentioned. 
Also the meningitis caused by the other pyogenic 
cocci usually is secondary to some other suppura- 
tive focus, often the middle ear; that caused by 
the organisms of typhoid, glanders, plague and 
influenza occurs during the course of the diseases 
caused by the corresponding micro-organisms. 

Previous to 1887 diplococci resembling the pneu- Micrococcus 

r ° r Meningitidis. 

mococcus had been found in the exudate in cases 
of cerebrospinal meningitis by Foa and Bordoni- 
Unreduzzi, by Fraenkel and others. Weichsel- 
baum made similar observations during the same 
year, and in addition described six cases in which 
a diplococcus of another nature was present in 
pure cultures. To the latter he gave the name of 
Diplococcus intracellularis meningitidis. Exten- 
sive observations by others, both in Europe and 
America (Councilman, Mallory and Wright, and 
others), revealed the presence of the last-named 
organism in many instances, and showed that it is 
the most common cause of epidemic cerebrospinal 
meningitis. 

The meningococcus resembles the gonococcus 
closely in that it is usually found in biscuit-shaped 



£90 INFECTION AND IMMUNITY. 

pairs, nearly always within pus cells, and does not 
stain by Gram's method (Weichselbaum). It is 
properly to be called a micrococcus since it divides 
in two transverse directions (Albrecht and Gohn) ; 
tetrads, small groups and short chains are some- 
times seen. However, it forms no striking chains, 
is non-motile and produces no spores. Growth 
may be obtained on some of the ordinary media 
(glycerin agar), in which the organism differs 
from the gonococcus, but a medium which contains 
blood or serum is much more favorable. It is an 
obligate aerobe, grows best at the body tempera- 
ture and virulence is soon lost under artificial 
conditions. 

Resistance. It produces a membrane on meat broth with 
clouding of the medium. Viability is retained 
only for a few days at room temperature. When 
dried on paper and exposed to the sunlight it lives 
no longer than twenty-four hours, in a dark room 
seventy-two hours (Councilman, Mallory and 
Wright). It is killed by a temperature of 65° C. 
for thirty minutes (Albrecht and Gohn). 
virulence; The meningococcus has little virulence for ani- 

Endotoxm. ma i s# When injected in sufficient quantity into 
the peritoneal or pleural cavity of white mice 
death results in from twenty-four to forty-eight 
hours, but not when given subcutaneouslv. Men- 
ingitis may be produced by subdural injections, 
but the disease does not resemble the epidemic 
meningitis of man. So far as is known at the 
present time the organism does not produce a 
soluble toxin, but possesses rather an endotoxin. 
infection Although the disease is usually spoken of as a 
Atria, primary meningitis, there is reason to believe that 
it is secondary to an acute rhinitis or acute in- 



MENINGOCOCCUS. 391 

flainniation of the accessory sinuses or middle ear, 
in many instances. From these places the coccus 
may readily reach the meninges by way of the 
lymphatic channels. It has been found repeatedly 
in the noses of those who were associated with 
cases of the disease; in such cases an acute rhi- 
nitis may be present without the subsequent de- 
velopment of meningitis. Clinical histories show 
that the infection commonly is preceded by 
acute rhinitis. The inflammation in the meninges 
is always cerebrospinal in its distribution and 
is characterized by a purulent or fibrino-purulent 
exudate in which the diplococci are present in 
varying quantities. Diagnosis may often be estab- 
lished clinically by the microscopic or cultural 
examination of the cerebrospinal fluid which is 
removed by lumbar puncture. 

Acute encephalitis, acute bronchitis, lobar pneu- complications 
monia and acute arthritis have been observed as f n n f^Jns. 
complications, in which organisms resembling the 
meningococcus have been found in a number of 
instances. An accompanying bronchitis, lobar or 
lobular pneumonia may be caused by mixed infec- 
tion with other organisms (pneumococcus, strepto- 
coccus, staphylococcus). Since it would be diffi- 
cult to explain some of these complications except 
on the basis of metastasis, it seems very probable 
that the organism reaches the blood stream. Micro- 
cocci resembling the meningococcus have been 
found in acute bronchitis, rhinitis, lobular pneu- 
monia and conjunctivitis, in the absence of cere- 
bral involvement, and it is possible that it may be 
the cause of independent inflammations in these 
tissues. Weichselbaum, however, is inclined to 
doubt the identity of such organisms with the 



392 



INFECTION AND IMMUNITY. 



Transmission 
and Contag- 
iousness. 



Susceptibility 
and Immunity. 



meningococcus. Particularly in cases of bronchi- 
tis and lobular pneumonia the coccus may be con- 
fused with the Micrococcus catarrhalis of Pfeifler, 
with which it is identical morphologically. 

The extent to which the meningococcus is a 
normal inhabitant of the nasal mucous membrane 
is unknown. 

Since the organism seems to be excreted chiefly 
or only with the nasal discharges, the latter prob- 
ably are important for transmission of the infec- 
tion. Because of the low resistance of the organ- 
ism to desiccation and light, transmission prob- 
ably is a fairly direct one. This is suggested also 
by the occasional occurrence of epidemics in insti- 
tutions. Contagiousness is of a rather low order ; 
this is indicated by the distribution of the 111 
cases observed by Councilman, Mallory and 
Wright in Boston, the city being somewhat dif- 
fusely infected with very little tendency of the dis- 
ease to occur in groups of individuals or in several 
members of a family. 

The desirability of avoiding contact with the 
infected is evident; special prophylactic meas- 
ures are not known. In the presence of an epi- 
demic the treatment of rhinitis with local antisep- 
tics would suggest itself. 

Children and young people are particularly sus- 
ceptible to both epidemic and sporadic infections 
with the meningococcus. Exposure incident to the 
cold and variable weather of the winter and spring, 
in which seasons the disease prevails, may be in- 
fluential in lowering resistance. Second attacks 
are rare, Councilman, Mallory and Wright col- 
lecting only five such examples from the literature. 
Lipierre immunized animals with cultures and 



INFLUENZA. 393 

with a toxin, the latter being a glycerin extract of 
old cultures. Their resistance to infection was 
said to be increased, and the serum of highly im- 
munized animals was antitoxic, preventive and 
curative for other animals. Corroborative work 
is lacking. According to Davis, the serum in 
cases of epidemic meningitis shows an increased 
bactericidal power for the coccus on the thirteenth 
day of the disease; the agglutinins which develop 
probably persist for some time, but are little above 
the normal after two and one-half years. 1 Fairly 
strong agglutinins may be obtained by the im- 
munization of rabbits (Jager and Albrecht and 
Gohn). 

VII. INFLUENZA. 

Influenza occurs sporadically and in epidemics 
of greater or less proportions. Its extreme con- 
tagiousness is shown by the striking rapidity with 
which it spread over the whole civilized world in 
the epidemic of 1889 and 1890, leaving behind it 

1. The conclusions of Dr. Davis are as follows : In five 
cases of epidemic cerebrospinal meningitis, the meningococcus 
( Weichselbaum type), was obtained in every case from the 
cerebrospinal fluid, and in one case from the nose and 
sputum by cultures. In the other four cases Gram-negative 
diplococci suggestive of either meningococcus or Micrococcus 
catarrhali8 were seen in smears, but were not recovered in 
cultures. Agglutination of meningococcus by the serum of 
patients with meningitis occurs in a dilution of 1-5 or higher. 
The meningococcus grows in some deflbrinated normal bloods, 
but not in others, there being thus an interesting individual 
variation. In the blood of three meningitis cases it did not 
grow. Normal human serum is distinctly bactericidal toward 
the meningococcus. This property is increased in sera of 
meningitis cases, and is diminished, but not entirely de- 
stroyed by heating to 60 C. for thirty minutes. Cerebro- 
spinal fluid acts in much the same way as heated serum. 
The opsonin content of the blood does not appear to be 
altered during the course of epidemic meningitis. Normal 
cerebrospinal fluid does not contain opsonin for meningococci. 
— Jour, of Infectious Diseases, 1905. vol. ii. 



394 



1XFECTI0X AXD IMMUNITY. 



Bacillus 
Influenza?. 



a trail of lesser epidemics which have prevailed up 
to the present time. 

During the epidemic just cited a number of or- 
ganisms were erroneously described as the cause of 
the disease. In 1892, however, Pfeiffer discovered 
a minute bacillus which he found constantly and 
in large numbers in the sputum of influenza pa-v 
tients only. The observations of Pfeiffer have 
been confirmed by a large number of investigators, 
and the organism, Bacillus influenza', is now ac- 
cepted as the cause of the disease. It is one of the 
smallest of bacteria (0.2 or 0.3 by 0.5 microns), is 
non-motile and forms no spores. A medium con- 
taining blood or hemoglobin is essential for its 
artificial cultivation, and even under the best con- 
ditions it grows meagerly and slowly. A number 
of bloods, but particularly those of man and the 
dove, favor its growth. It is a strong aerobe. The 
organism is best stained by a dilute solution of 
carbol fuchsin (1 to 10), and, like the plague 
bacillus, exhibits polar staining, i. e., the ends 
stain more deeply than the central portion. 
Symbiosis. When the staphylococcus and some other organ- 
isms are grown in mixed culture with the influ- 
enza bacillus, the latter is stimulated to a more 
vigorous growth. According to Jacobsohn, killed 
cultures of the streptococcus greatly increase the 
virulence of the influenza bacillus when the mix- 
ture is injected into animals. 

Pfeiffer designates as pseudoinfluenza bacilli a 
number of influenza-like organisms which have 
been found in man and animals. They have the 
morphology of the influenza bacillus, are a little 
larger, and also prefer a medium which contains 
hemoglobin, but since some of them occnr in ani- 



Pseudo- 

Influenza 

Bacilli. 



INFLUENZA. 395 

mals which are known not to be susceptible to in- 
fluenza, it is concluded that they can not be identi- 
cal with the influenza bacillus. The influenza-like 
bacillus which Jochmann and Krause consider as 
the cause of whooping-cough, may be mentioned 
in this connection. 

The resistance of the bacillus to desiccation, Resistance 

and Virulence. 

sunlight and unfavorable temperatures is very low. 
It dies in from twenty-four to thirty-six hours at 
room temperature, when contained in sputum, and 
lives for about thirty-two hours in hydrant water 
(Pfeiffer). It is not highly virulent for experi- 
ment animals, although a condition said to resem- 
ble influenza has been produced in monkeys by 
placing pure cultures on the nasal mucous mem- 
brane. Fatal infections may be produced by intra- 
venous inoculation of the bacillus into monkeys 
and rabbits, and killed cultures produce a fatal 
intoxication in rabbits. Virulent cultures in suffi- 
cient quantity produce fatal peritonitis in guinea- 
pigs. Since the bacilli seem not to proliferate 
when fatal quantities are injected intravenously 
into rabbits, and since fatal intoxication, without 
the occurrence of bacteriemia, may take place 
when a tracheal infection is induced in the ape 
(Pfeiffer), it is concluded that the toxic phenom- 
ena of influenza are due to the absorption of bac- 
terial toxins from the mucous surfaces. A soluble 
toxin has not been obtained in culture media. The 
organism is a facultative pus producer. 

So far as is known the influenza bacillus is ex- Distribution 
creted only with the secretions of infected surfaces, 
i. e., from the upper respiratory passages, con- 
junctiva, car, etc. The belief, commonly held, 
that the influenza bacillus does not enter the cir- 



396 INFECTION AND IMMUNITY. 

culation probably is erroneous. That metastatic 
infection is possible, by way of the lymph or blood 
channels, is shown by the occurrence of influenza 
meningitis, and, rarely, of influenza peritonitis 
(Hill and Fisch). According to Jehle, the influ- 
enza bacillus invades the blood very frequently in 
some of the acute exanthemata. It was found in 
the blood in 22 out of 48 cases of scarlet fever, in 
15 of 23 cases of measles, and in 5 of 9 cases of 
varicella (cited by Hektoen). Hence, these dis- 
eases would seem to create conditions favorable for 
invasion by this bacillus. When the bacilli reach 
the blood they probably are killed quickly. It is 
probable that the ordinary nervous phenomena of 
the disease are due to intoxication rather than to 
actual infection of the nervous structures. As To 
whether the symptoms of so-called intestinal in- 
fluenza are due to an invasion of the intestines 
by the bacilli or to a specialized action of circu- 
lating toxin seems not to have been definitely set- 
tled. There certainly is abundant opportunity for 
infection of the intestines in cases of bronchial 
influenza. In the bronchitis of influenza the or- 
ganisms are found in large numbers in the smaller 
bronchial tubes, both free and within leucocytes, 
hence, in searching for the bacilli clinically it 
should be certain that the sputum. examined repre- 
sents the bronchial exudate. In influenza pneu- 
monia, which usually is of the lobular type, the 
bacilli, mixed with pus cells and contained in 
them, are found in large numbers in the alveoli. 
Pure cultures of the bacillus have been obtained 
from cases of conjunctivitis, and they occur not 
infrequently in middle-ear complications which 
develop during the course of the disease. Influ- 



IX FLU EX Z A. 



397 



cnza conjunctivitis sometimes occurs in epidemic 
form, particularly in institutions and schools. 

Pneumonic foci which develop during influenza 
frequently show the pneumococcus, and sometimes 
the streptococcus or the bacillus of Friedlander in 
addition to the influenza bacillus, and similar 
mixed infections occur in pleurisy and in middle- 
ear disease. Influenza may be superimposed on 
other infections; individuals suffering from pul- 
monary tuberculosis are particularly susceptible to 
influenza, and in them the prognosis is unfavor- 
able. 

The disease is transmitted directly from man to 
man and, chiefly, it is supposed, by means of in- 
fected droplets of sputum which are expelled in 
coughing and sneezing. Obviously kissing affords 
opportunity for infection. Infection by indirect 
contact is of less importance because of the rapid 
death of the bacillus after it leaves the body, but 
living germs may well be disseminated by soiled 
handkerchiefs or other contaminated linen. Dust 
infection possibly is of minor consequence. Chronic 
influenza in which the bacilli may persist in the 
bronchi for weeks, and cause recurrent acute at- 
tacks, is of importance for the maintenance of an 
epidemic. In tuberculous cavities the bacilli may 
flourish for long periods. 

Primary infection takes place in the upper res- 
piratory passages, and the disease extends readily 
from one surface to another, as from the nose to 
the pulmonary tissue. Infection of the ear usually 
is a complication of pharyngeal or pulmonary in- 
fection. Occasionally an influenza conjunctivitis 
is found without other localization. "Primary" 
infection of other organs, as the brain and perito- 



Mlxed 
Infections. 



Transmis- 
sion, Infec- 
tion Atria 
and Proph- 
ylaxis. 



398 INFECTION AND IMMUNITY. 

neum, are metastatic, although the original focus 
or atrium may not be observed. 

Little or nothing can be done in the way of 
general prophylaxis. Washing of the nose and 
mouth with antiseptics during an epidemic may 
reasonably be practiced, but with what success is 
uncertain. The aged and those of low vitality 
should avoid exposure to infection, for in them the 
severer complications, such as pneumonia, are 
more likely to occur. When influenza conjuncti- 
vitis appears epidemically in schools, the latter 
should be closed or the infected children excluded. 
immunity, Sus- Although little or nothing is known concerning 
Recurrences, the possibility of a natural immunity in man, ex- 
perience teaches that he is, on the whole, very sus- 
ceptible. The belief expressed by some that nurs- 
ing children are less susceptible than older people 
seems to have some foundation, although it is well 
known that they are not entirely immune. Influ- 
enza is sometimes cited as an infection in which 
one attack creates a predisposition for a second, 
but the truth of this is doubted by many who have 
had extensive experience with the disease. Wutz- 
dorff, in a study of the epidemic which prevailed 
in Germany during 1891-92, finds in the small 
number of cases, the irregularity of their distribu- 
tion, and comparative exemption of rather large 
districts, reasons for believing that one attack con- 
fers a degree of acquired immunity ; that is to say, 
the population had been so thoroughly infected 
(durchgeseucht) during the preceding year or two 
that comparatively few remained who were sus- 
ceptible, although the disease itself appeared to be 
more malignant than in the previous year (cited 
from Beck). However, the occurrence of second 



CH AX CROW. 



399 



attacks shortly after the first, and of repeated in- 
fections in some individuals indicate that acquired 
immunity is of short duration. The aged, those 
of low vitality, and those with pulmonary tuber- 
culosis, have low resistance to infection. 

Although Delius and Kolle were able to produce 
a slight increase in the resistance of guinea-pigs 
by the intraperitoneal injection of cultures, noth- 
ing like a well-marked immunity was obtained; 
nor did the serum of immune animals or convales- 
cent man show increased protective power for 
other animals. Slatineano, however, obtained 
serum of some protective value for guinea-pigs, 
by the immunization of rabbits and guinea-pigs, 
but it had no curative effect. The results of Can- 
tani were similar, and both observers noted the de- 
velopment of bactericidal power, as determined by 
the Pfeiffer reaction, and of agglutinins. At the 
present time there seems little to hope from vac- 
cination. 

There is said to be some increase in agglutinins 
in man as a consequence of infection. The agglu- 
tinating power of the serum of an immunized ani- 
mal may be as high as 1 to 500 (Cantani). 



Serum 
Properties. 



VIII. SOFT CHANCRE. 

The independence of soft chancre and syphilis, 
and the infectiousness of the former by inoculation 
with the purulent secretions of the ulcers, were 
established long ago. Rollet found that filtered 
pus lost its infectiousness. 

A large number of observers had found bacteria ^^n^ ■ 
of one kind or another in the pus and in stained ofDucre v 
sections of the walls of the ulcers, and probably 
some of them (e. g., Fnna), had skm the bacillus 



400 INFECTION AND IMMUNITY. 

which Ducrey described (1889) and later culti- 
vated, and which is now proved to be the cause of 
the disease. The bacillus is very small (0.4x1.5 
microns), is non-motile and shows polar staining. 
It resembles the plague bacillus in form, but is- 
somewhat smaller, and does not show the exten- 
sive involution forms of the latter. In the ulcer 
it lies singly, in small groups, or more characteris- 
tically in the form of bands, made up of two or 
more parallel chains, which infiltrate the wall of 
the ulcer. Large numbers are often found in the 
polymorphonuclear leucocytes of the pus, par- 
ticularly at an early stage of the lesion (Kroeft- 
ing). Great difficulty was encountered in culti- 
vating the bacillus, and Ducreyi first success was 
obtained with a medium which contained human 
skin. It has since been cultivated on agar which 
contains the blood or serum of man, rabbit or 
dog. Himmel attempted to cultivate it in the 
fresh defibrinated blood of the guinea-pig, but 
was unsuccessful because the bacilli were phago- 
cytized by the leucocytes (Babes). 

An ulcer resembling that of soft chancre may 
be produced in the ape, and also in the cat, by the 
inoculation of pure cultures. Didey reinoculated 
man, successfully, from the ulcers of the cat. 
When living cultures are injected into the guinea- 
pig (peritoneal cavity, subcutaneous tissue, dura 
mater), the bacilli are quickly taken up by leuco- 
cytes and digested (Himmel). Himmel reports 
having so decreased the resistance of guinea-pigs 
by peritoneal injections of lactic acid that they 
became susceptible to infection. After two or 
three passages the culture became so virulent that 



CAPSULATED BACILLI. 401 

fatal bacteriemia was caused without previously 
lowering the resistance of the animals. 

In man the infection is transmitted to the in- 
guinal lymph glands, but never becomes general. 

One attack in man does not confer lasting im- 
munity. Spontaneous recovery occurs, but its 
cause is not known. Inasmuch as the bacilli are 
found within leucocytes, phagocj^tosis may be a 
factor in recovery. The readiness with which the 
autoinoculation of adjacent skin takes place, even 
after the disease has existed for some time, sug- 
gests that general immunity is not established. 

IX. BACILLUS OF FRIEDLANDER AND OTHER MEM- 
BERS OF THE CAPSULE-FORMING GROUP. 

The bacillus of Friedlander, or Bacillus pneu- capsuiated 
monice, is the type of a rather large group of bac- Bac,,l, • 
teria, called the Friedlander group, or the group 
of Bacillus mucosus capsulatus. In addition to 
the ability to produce a mucus-like capsule or en- 
velop, they have in general the following charac- 
teristics (Abel) : short, plump rods, varying in 
their proportions, having no motion, no nagella, 
no spore formation, and not staining by Gram's 
method. They form mucus-like masses in cul- 
tures, do not liquefy gelatin and are facultative 
anaerobes. They are widely distributed in nature, 
vary from innocuousness to extreme pathogenicity 
for animals, are rarely found in the mouth, nose 
and bronchi normally (bacillus of Friedlander), 
one type being a normal inhabitant of the intes- 
tines, especially in children (B. laciis aerogenes). 
Perkins has been able to classify the members of 
this group on the basis of their fermenting powers 
for lactose and saccharose. He found their viru- 



402 



INFECTION AND IMMUNITY. 



Bacillus. 






lence for animals, immunization and agglutination 
tests, too variable to serve as bases for classifica- 
tion. In man three members of the group — they 
may be the same organism or variations of a type 
— are of interest from the standpoint of infection : 
Bacillus of Friedlander, the bacillus of rhinoscle- 
roma and the ozena bacillus. 
Pneumonia In 129 cases of acute inflammation of the lungs, 
FrietNander's Weichselbaum found the bacillus of pneumonia 
nine times, twice with streptococci and once with 
the diplococcus of pneumonia. The organism 
causes lobular pneumonia more frequently than 
lobar. The homogeneous non-granular surface, 
and the large amount of fluid of a viscid or mu- 
cous consistence, are characteristic anatomic feat- 
ures. The alveoli contain massive numbers of the 
bacilli. The bacillus of Friedlander is found also 
as the cause of pyelitis, cystitis, pyelonephritis, 
serous or purulent pericarditis, pleuritis and 
meningitis, which may be accompanied by brain 
abscesses. Meningitis when produced by this or- 
ganism usually or always is secondary to infection 
in other parts of the body by the same organism 
(middle ear and accessory sinuses of the nose). 

An organism of the Friedlander type is found 
with few exceptions in the tissues in rhinoscle- 
roma, and by many is considered as the cause of 
the condition. A similar organism is found con- 
stantly in the secretions and crusts in ozena. 

Antiserums of distinct power have not been ob- 
tained for members of the group. Prolonged im- 
munization with some strains yields an agglutinat- 
ing serum of low value. The agglutination re- 
action is of no value for identification of the dif- 
ferent members of the group, nor for clinical 
diagnosis. 



Rhinoscleroma 
and Ozena. 






RELAPSIXG FEVER. 403 

X. RELAPSIXG FEVEK. 

In 1868 Obermeier discovered in the blood of The Parasite. 

patients suffering from relapsing fever, "very fine 
threads exhibiting motility" ; these "threads" have 
since been known as the Spirocheta obermeieri.* 
and are recognized as the cause of the disease. 
They are very thin (about 1 micron), from 10 to 
40 microns in length, and of spiral form. Three 
types of motion are described : a screw-like, a for- 
ward and backward movement and a lateral bend- 
ing. They are found only in the blood and blood- 
forming organs. They disappear from the blood 
with remarkable rapidity at the time of crisis, al- 
though they may be found in the spleen one or 
two days later. 

The organism has not been grown artificially, 
but it may be kept alive for a number of days in 
the blood or serum of patients. As the micro-or- 
ganisms die agglomerations are formed and they 
undergo granular changes. 

The organism is not found in Nature, and, Transmission 
since it occurs only in the blood of the sick, it has 
long been assumed that infection can be accom- 
plished only by the inoculation of infected blood. 

* This organism is sometimes called a spirillum, incor- 
rectly. The spirillaceae, Migula's third family under the 
Order of Eubacteria, comprises organisms with these char- 
acteristics : "Cells which are twisted screw-fashion or repre- 
sent a segment of a spiral. Division takes place only in one 
direction of space after the cell has elongated." The dif- 
ference between spirillum and spirochaeta is shown by the 
following : "3. Genus : Spirillum. Cells rigid, with polar 
tufts, for the most part bent in the form of a half-circle, 
as organs of locomotion. 4. Genus : Spirochaeta. Cells with 
snake-like bending, organs of locomotion unknown." 
Although Migula classes this organism with the bacteria, 
there is some ground for considering it protozoon in nature. 



404 INFECTION AND IMMUNITY. 

The parasites have been demonstrated repeatedly 
in bedbugs which are found on the mattresses of 
the sickbed, and monkeys have been infected by 
inoculating them with the blood found in the 
bodies of these insects, and by the bites of the lat- 
ter (Tictin). It is said that they may remain 
alive in bedbugs for as long as thirty days. It is 
not altogether excluded that other vermin also 
transmit the disease. 

The spirocheta does not appear in any of the ex- 
cretions, unless they happen to be of a bloody 
character. 

Certain monkeys, those belonging to the slender- 
nosed family (Catarrhince), may be infected by 
injecting the blood of patients, provided the blood 
used is taken during the paroxysm, i. e., at a time 
when the microbes are known to be in the blood. 
Monkeys do not contract the disease under natural 
conditions. Other animals are not susceptible. 
The incubation period in man usually is from five 
to seven days, and in monkeys from one and one- 
half to four days. Cloudy swelling of the paren- 
chymatous organs, ecchymoses and infarcts of the 
spleen and kidneys are found in fatal cases. 

Prophylaxis consists in isolation of the patient, 
cleanliness, and the destruction of vermin, espe- 
cially bedbugs. 

Relapsing fever occurs in various races of man, 
and so far as known none are immune. Osier states 
that in the United States the disease has not been 
seen since 1869, when it was epidemic in New 
York and Philadelphia. The natural immunity of 
other animals is referred either to phagocytosis 
or to normal bacteriolysins, but the conditions 
probably are not thoroughly understood. 



RELAPSING FEVER. 



405 



Phagocytosis 
and Bacterio- 
lysins. 



As stated above, a remarkable feature in the 
course of the disease is the rapidity with which the 
micro-organisms disappear from the blood at the 
time of the crisis. Metchnikoff refers this to 
phagocytosis by the microphages, which undergo 
a progressive increase during the paroxysm and 
decrease after the crisis. Very little phagocytosis 
appears to take place in the circulating blood, but 
in the spleen many spirochetae are found within 
polymorphoneuclear leucocytes. Tictin also found 
them in the parenchymatous cells of the kidney, 
liver and lungs. Phagocytosis is most marked at or 
near the time of the crisis. According to Metchni- 
koff, relapse or reinfection is accomplished by 
spirochete which again invade the body from the 
spleen. 

Eussian observers have studied the development 
of a specific bactericidal power in the serum of the 
sick and in animals which were immunized by the 
injection of infected blood from man. Inasmuch 
as the organism can not be cultivated, bactericidal 
tests must be performed with the organisms as 
they occur in the blood or serum of the patients, 
and Gabritschewsky has devised a technic for this 
procedure. 

A drop of serum from an immune animal or a Technic 
convalescent patient is mixed on a slide with a 
drop of serum which contains the spirocheta, the 
latter serum being taken from a patient during an 
attack. The preparation is sealed under a cover- 
glass and examined at intervals, and the death of 
the organisms is determined by their loss of mo- 
tility. It is said that the bactericidal power of 
human blood following infection, and that of im- 
munized animals, is increased. 



406 INFECTION AND IMMUNITY. 

a d C p' v ^ n v * ew °^ ^ e "^ ac * s ^ a * ^ nree or mor e relapses 
sive immunity, may occur and that reinfection is possible at a 
later period, it seems probable that man does not 
readily acquire immunity to the infection, al- 
though second and third relapses are said to be 
lighter than the first. Monkeys which have been 
artificially infected several times acquire some 
resistance to the disease. The view of Metch- 
nikoff that the spleen is essentially involved in 
recovery and immunity seems to have been dis- 
proved by the experiments of Tictin, who found 
that splenectomy had no influence on recovery or 
the development of immunity. 

The serum of convalescents affords a certain de- 
gree of protection to the monkey (G-abritschew- 
sky) . Loventhal utilized the serum of immunized 
horses in the treatment of the disease in man, and 
reported a decrease in the number and severity of 
relapses. The action of the serum has been re- 
ferred both to its content in bactericidal antibodies, 
and to its ability to stimulate phagocytosis. 

Melkich states that agglutinins are formed and 
that they appear on from the third to the fifth 
day of the disease. 



A rapidly fatal disease of geese, spirocheta septi- 
cemia, or spirillosis of geese, is caused by an or- 
ganism which resembles the spirocheta of Ober- 
meier, and a similar infection has been noted in 
chickens in Brazil and in cattle in the Transvaal. 



GEOUP IV. 



Infectious diseases which usually are chronic, 
but may run acute courses. They are characterized 
by marked local tissue changes, which exert a lim- 
iting influence on the processes, and include the 
infectious granulomata, excepting syphilis. Infec- 
tion produces little or no immunity. In some in- 
stances the prolonged immunization of animals in- 
duces increased resistance to infection (tuberculo- 
sis) ; in other instances this has not been deter- 
mined, or is difficult of determination because of 
the non-susceptibility of experiment animals to 
the corresponding infections. The serums of im- 
munized animals, in so far as this subject has been 
investigated, show little or no protective or cura- 
tive power. 

I. TUBERCULOSIS. 

Klemke, in 1843, but more particularly Ville- 
min, in 1865, demonstrated the infectiousness of 
tuberculosis by animal experiments, and these re- 
sults were substantiated later by' such investigators 
as Klebs, Chauveau, Baumgarten and Conheim. 
Baumgarten first saw the tubercle bacillus in sec- 
tions of tuberculous material from which the tis- 
sue cells had been dissolved by potassium hydroxid, 
and at almost the same time Koch succeeded in 
demonstrating its presence in all tuberculous 
lesions by a special staining method. He eventu- 
ally obtained the organism in pure cultures with 
which he again produced tuberculosis in experi- 
ment animals. 

The tubercle bacillus is an obligate aerobic para- 
site, has the form of a slender, non-flagellated rod, 



408 



INFECTION AND IMMUNITY. 



Characteristics 
of the Bacillus. 



Staining 
Properties. 



often slightly curved, from 2 to 4 microns long 
and from 0.3 to 0.5 microns broad. In stained and 
even in unstained specimens, when properly 
treated, a number of spherical, oval or elongated 
clear spaces can be seen which Koch at one time 
thought to be spores. They are now considered 
either as vacuoles, or as representing some form of 
degeneration or reserve nutritious material. Spore 
formation is uncertain. The organism is sup- 
posed to possess a membrane which may be re- 
sponsible for its strong resistance against heat and 
desiccation. Feinberg speaks of a nucleus ( ?) which 
may be demonstrated by a modified Komanowsky 
stain. The organism shows many variations in its 
morphology under different conditions. It often 
exists in isolated clumps, either in cultures or in 
tissues, and may be excreted as such in the urine. 
In certain cultures and sometimes in animal tis- 
sues it grows in the form of longer or shorter 
branching threads, in this respect resembling acti- 
nomyces. This last occurrence has led a number 
of authorities to class the tubercle bacillus as a 
streptothrix, while others would give it an inter- 
mediate position between true bacteria (schizomy- 
cetes) and the streptothrix (a hyphomyces). Oval 
or spherical degeneration forms, the capsules or 
corpuscles of Schron, are found in advanced tuber- 
culosis of the lymph glands and other organs in 
which there is a great deal of necrosis. 

The tubercle bacillus is one of a group of organ- 
isms which are said to be "acid fast" in their 
staining properties. When stained with the carbol 
fuchsin of Ziehl and subjected to the action of 
mineral acids in dilute solutions the fuchsin is not 
removed. After counterstaining with methylene 



TUBERCULOSIS. 409 

blue, the tubercle bacilli appear red, whereas other 
organisms, not "acid fast," are stained with the 
methylene blue. It is not difficult to recognize the 
bacilli in sections of tissue when the proper technic 
is used, although the search is at times a laborious 
one. ■ In old processes the organism often can not 
be recognized, and recourse to animal inoculation 
may be necessary in order to demonstrate the ex- 
istence of tuberculosis. 

It is ordinarity a difficult task to obtain the Cultivation. 
tubercle bacillus in pure culture, the technic of 
which we need not consider. Even under the best 
conditions growth is very slow, and may not be 
recognizable to the naked eye for from six to ten 
days. Coagulated serum of the cow to which has 
been added from 2 to 4 per cent, glycerin is the 
most favorable culture medium. Good growth oc- 
curs also in glycerin agar, in glycerin bouillon 
and on potatoes. The optimum temperature is 37° 
C. ; growth does not occur above 42° C. nor below 
30° C. When a small amount of culture is planted 
on the surface of glycerin bouillon it proliferates 
slowly to form a heavy membrane. In time this 
growth sinks from its own weight and a new mem- 
brane forms. This process continues until large 
masses have accumulated at the bottom of the 
flask. 

In its resistance to desiccation the tubercle ba- Resistance. 
cillus is exceeded only by spore-forming organisms ; 
it lives approximately for three months in dried 
sputum which appears to form a protective coat- 
ing about it. Direct sunlight destroys it in a few 
hours at the most, whereas diffuse light kills it 
only after from five to seven days (Koch). It is 
said that the guinea-pig when exposed to sunlight 



410 INFECTION AND IMMUNITY. 

withstands tuberculosis for a longer time than one 
which is kept in the dark. Eoentgen rays are bac- 
tericidal for the organism, killing it in about one 
hour (Eieder). Under moist heat a temperature 
of 55° C. kills it in from four to six hours, 60° C. 
in one hour, 70° C. in from ten to twenty minutes, 
80° C. in five minutes, from 90° to 95° C. in from 
one to two minutes. When embedded in sputum 
it is more resistant, five minutes being required to 
kill it at the boiling temperature. Corrosive sub- 
limate is not a good disinfectant in this case, inas- 
much as it produces an albuminous precipitate 
around the organism which prevents penetration 
of the sublimate. Five per cent, carbolic acid 
added to equal parts of sputum kills the bacillus in 
twenty-four hours. Formalin vapor is a good dis- 
infectant for dry, but not for moist sputum. Iodo- 
form is not a good disinfectant, in spite of its bene- 
ficial influence on the infectious process. The re- 
sistance of the bacillus to gastric digestion has an 
important bearing on the occurrence of infection 
in the intestinal tract. The gastric juice of the 
dog, in one instance, failed to kill the bacillus after 
six hours' exposure, although it had the power of 
prohibiting proliferation. 
virulence. The bacillus of human tuberculosis, although 
fairly constant in its virulence, may be attenuated 
by various means. Its prolonged existence in putrid 
sputum decreases its virulence and a similar de- 
crease occurs on potato, in old cultures or in those 
which contain iodoform, boracic acid and some 
other substances. Inoculation with such cultures 
produces a chronic form of tuberculosis in animals 
which may heal. In other instances cultures which 
have grown on artificial media for many years re- 
tained their original virulence. 



Products. 



TUBERCULOSIS. 411 

The organism contains about 90 per cent, of 
water. One-fourth of a dried bacterial mass may 
be extracted as a wax-like or fat-like substance by 
a mixture of alcohol and ether. The acid-fast 
staining property of the bacillus depends on this 
substance. The remaining portion of the mass, 
consisting largely of proteins, which may be ex- 
trated by dilute alkalies, contains a toxic nucleo- 
albumin. Cellulose, representing a portion of the 
capsular substance, is also found in the residue. 

Killed cultures when given subcutaneouslv pro- Toxic 
duce necrosis, abscesses, caseation, marasmus, and 
a subnormal temperature. When given to rabbits 
and guinea-pigs intravenously they cause rapid 
emaciation and death in from a few days to a few 
weeks. By beginning with very minute doses, how- 
ever, the animals may be gradually habituated to 
intoxication by the dead bacilli and eventually 
withstand large doses. The same holds true of the 
various toxic substances, including tuberculin, 
which may be extracted from cultures. The pro- 
teins and alkaline extracts cause abscesses when 
given subcutaneously. The fever-producing sub- 
stance which is present in the preparations men- 
tioned below is one of the metabolic products of 
the bacillus, rather than a constituent of the bac- 
terial cell (Koch). This substance is 100 times 
as toxic for tuberculous animals as for healthy and 
causes an increase in the eosinophiles of the blood. 
In addition to the fever-producing substance, 
Maragliano and others recognize as a constituent 
of the bacillus a heat susceptible "toxalbumin" 
(destroyed at 100° C.) which reduces temperature. 
Hammerschlag speaks of a toxin which in animals 
causes fatal convulsions. The toxic products of the 



412 INFECTION AND IMMUNITY. 

tubercle bacillus show their greatest toxicity when 
injected into the brain, and this method of injec- 
tion has been suggested for the standardization of 
tuberculin. 

Tuberculin. Of the toxic preparations of the bacillus the 
greatest interest attaches to tuberculin which 
Koch, in 1891, announced as an agent which could 
be used for the specific diagnosis of tuberculosis 
and which, when properly administered, had cer- 
tain curative effects. Its preparation is simple. 
Cultures are allowed to grow for four weeks in 
peptone bouillon which contains 5 per cent, of 
glycerin. At the end of this time the organisms 
are killed by exposure to a temperature of 100° C. 
for one hour (Marx) . The fluid is reduced to one- 
tenth its original volume by evaporation under a 
vacuum at a low temperature and the bacterial 
cells are eventually removed by filtration. The 
percentage of glycerin which is present in the final 
preparation acts as a preservative, but 0.5 per 
cent, carbolic acid may be added in addition. The 
active substance in tuberculin may be precipitated 
by 66 per cent, alcohol; its chemical nature re- 
mains unknown. 

•ta," "tr" In addition to the "old tuberculin," which has 
just been described, Koch has made several other 
preparations having similar properties, the use of 
which has been proposed for diagnostic and cura- 
tive purposes and for convenience in carrying out 
the agglutination reaction. One of these, "TA," 
is an alkaline preparation which is made by ex- 
tracting cultures with 1/10 normal sodium hy- 
droxid solution. Its value as a diagnostic was 
equal to or exceeded that of tuberculin because of 
the longer duration of the reaction. In view of 



'TO.' 



TUBERCULOSIS. 413 

the fact, however, that it contained undissolved 
cells, which caused the formation of abscesses at 
the point of injection, its nse was not encouraged. 
For purposes of immunization Koch prepared a 
fluid which contained all the bacterial constituents 
and which at the same time is readily absorbed 
without abscess formation. For its preparation 
dried masses of the organism are ground up in an 
agate mortar; after suspension in distilled water 
and centrifugation, the emulsion consists of two 
layers. The overlying opalescent whitish fluid was 
designated as "TO" (Tuberculin-Obers) . After 
removal of the fluid from the precipitate the lat- 
ter was again dried and ground, suspended in 
water and centrifugated as before, and the process 
repeated until none of the sediment remained. The 
different fractions of fluid, except the "TO," were 
combined to constitute "TB" (Tuberculin-Rest) , 
which is really an emulsion of minute fragments 
of cells. It is readily absorbed and does not cause 
the formation of abscesses. This is commonly 
called Koch's "new tuberculin." Still another 
preparation which Koch has recently devised for 
active immunization and for convenience in per- 
forming the agglutination test consists of dried 
and ground up bacilli which are suspended in 
equal parts of glycerin and water, Neutuberculin 
Koch (Bazillenemusion) . 

Preparations which in many respects are analo- other 
gous to those of Koch have been made by different 
investigators; the tuberculocidin of Klebs, the tu- 
berculins of de Schweinitz and Porset and that of 
Denys, the two toxins of tuberculins of Maragliano, 
which he utilizes for the preparation of antitoxic 
serums, the oxytuberculin of Herschfelder, the 



Tuberculins. 



414 INFECTION AND IMMUNITY. 

"TD" and the "TDK" of Behring and the tubercu- 
loplasmin of Buchner. Marmorek claims to have 
obtained the true toxin of the tubercle bacillus by 
growing young, vigorous cultures on a complicated 
medium, denying that tuberculin represents the 
true toxin of the organism. 
standard- Tuberculin can not be standardized with accur- 
acy. Because of the extraordinary susceptibility of 
tuberculous animals to tuberculin, Koch decided to 
estimate its value by the quantity required to kill 
such animals. From 0.5 to 1 c.c. of tuberculin, 
when injected into a healthy guinea-pig, causes 
neither a local nor a general reaction, whereas 
from 0.1 to 0.15 c.c. kills a tuberculous guinea- 
pig in from twenty-four to forty-eight hours. For 
standardization von Lingelsheim recommends in- 
tracerebral injection into healthy guinea-pigs, be- 
cause of the extreme toxicity of tuberculin when 
introduced into the central nervous system; only 
1/180 as much tuberculin was required to cause 
death by intracerebral injections as compared with 
subcutaneous or intraperitoneal. Behring bases the 
value of tuberculin on its toxicity for healthy 
guinea-pigs and in his terms the expression "1 
c.cm. = 1,000 M." means that one gram of the 
toxin is fatal to 1,000 grams of guinea-pig tissue. 
His "TD" has a value of 1,250 M., and "TDK," 
12,500 M. 
Dissemination. The tubercle bacillus undergoes no proliferation 
outside the body and its occurrence in nature de- 
pends on the distribution of the infected excre- 
tions, particularly the sputum, of man. Hence it 
is found most abundantly in the rooms and homes 
of patients and in tuberculous wards of hospitals. 
Reception of sputum on the handkerchief of the 



TUBERCULOSIS. 



415 



patient, where it subsequently dries, and its dis- 
charge on the floor in public places, where it quick- 
ly becomes pulverized, as in street cars, are condi- 
tions which favor dissemination and the infection 
of others. In unconfmed places which are exposed 
to the action of light and sun, as the streets and 
sidewalks, the danger is less on account of the 
shorter life of the organism under these conditions 
and the greater volume of surrounding air. The 
calculation of Heller that a tuberculous patient 
may excrete 7,200,000,000 of bacilli in a day sug- 
gests the number which may lurk in a single mis- 
placed portion of sputum. Sputum which is kept 
moist is not a source of particular danger, inas- 
much as ordinary currents of air do not dissipate 
it in the form of infected drops. Droplets of spu- 
tum which are expelled by coughing contribute 
greatly to the infected dust which surrounds a pr - 
tient. 

Large quantities of bacilli are often excreted Li 
the feces in intestinal tuberculosis and in the urine 
in genitourinary tuberculosis, or in general miliary 
tuberculosis with localization of the process in the 
urinary organs. The pus from tuberculous ab- 
scesses commonly is infectious. 

Great interest attaches to the possibility of infec- 
tion of man by the milk and meat of tuberculous 
cattle. Previous to 1901, through the work of 
Smith and others, the opinion had been gaining 
ground that the bacilli of human and bovine tuber- 
culosis are not identical. It was not always possi- 
ble to produce tuberculosis in cattle by feeding 
them or causing them to inhale tuberculous spu- 
tum or pure cultures which were highly infectious 
for other experiment animals, although bacilli of 



Dried 
Sputum 



Bovine 
and Human 
Tuberculosis. 



416 INFECTION AND IMMUNITY. 

bovine origin invariably caused the disease in cattle 
when administered in a similar manner. It seemed 
then that the two bacilli are not identical in their 
pathogenic powers. Koch having performed such 
experiments without being able to infect cattle with 
bacilli of human origin expressed his belief that 
the converse also is true, i. e.,that the bovine ba- 
cillus is not pathogenic for man. Perhaps the 
strongest argument in favor of this view is the 
circumstance that primary tuberculosis of the ines- 
tines and mesenteric glands is very rare in chil- 
dren, who drink a good deal of milk, in spite of 
the great prevalence of tuberculous cows. Many 
protests followed the announcement of Koch's 
views, and in a short time a number of investiga- 
tors showed, first, that it is possible in some cases 
to produce tuberculosis in cattle with tuberculous 
material from man, and, second, that infection of 
man with the bovine bacillus is possible. Un- 
questionable proof of the latter consists in the de- 
velopment of localized tuberculosis in those who 
have performed autopsies on tuberculous cattle 
(Kavanel and others). These occurrences, of 
course, do not prove the identity of the two organ- 
isms, for there is still abundant reason to believe 
that the two bacilli are most pathogenic for their 
respective, natural hosts, and much less pathogenic 
for the alternative hosts. Theobald Smith has 
pointed out that many experiments in which the 
pathogenicity of the human bacillus for cattle was 
investigated by the feeding of tuberculous sputum 
must be repeated, inasmuch as it was not deter- 
mined in advance whether the organism contained 
in the sputum was of the human or bovine type. 
Naturally, absolute conclusions as to the patho- 



TUBERCULOSIS. 417 

genicity of the human bacillus for cattle could not 
be drawn with this fact undetermined. In some 
cases the combined sputum from many patients 
has been fed to cattle, and, since both human and 
bovine bacilli may have been administered, the re- 
sults are valueless in relation to the point under 
discussion. In each instance the organism should 
be obtained in pure culture, its identity as a human 
or bovine bacillus determined and the experiment 
performed with such pure cultures. The following 
points serve to distinguish the bovine bacillus from 
the human: First, the bovine bacillus is shorter Differences in 
than the human; second, when first cultivated it 
grows feebly in media in which the human bacil- 
lus flourishes; third, it has a higher virulence for 
rabbits and guinea-pigs, and, fourth, it produces 
more extensive lesions in cattle. To these Smith 
has added a fifth point, which be has found to be 
distinctive in a large number of cultures. In 
bouillon which contains 5 per cent, of glycerin and 
which is 2 per cent, acid to phenol phthalein the 
bovine bacillus produces a neutral or faintly alka- 
line reaction in from three to several weeks, 
whereas the human bacillus, after causing tempo- 
rary alkalinity, produces a terminal acidity of 
from 0.5 to 1.5 per cent. On the basis of this test 
and other points the bacilli of two cases of mesen- 
teric tuberculosis in man were recognized as bo- 
vine in type. In view of the fact that infection of 
man with the bovine bacillus has been shown to be 
possible, we arc still justified in considering the 
meat and especially the milk of tuberculous cattle 
as the probable sources of infection in a limited 
number of cases. 

Comparatively few cases of undoubted congeni- 



418 INFECTION AND IMMUNITY. 

Congenital tal tuberculosis have been observed, and in such 
cases the mothers are usually in an advanced stage 
of the disease. It is probable that the organisms 
reach the fetus following metastatic invasion of the 
placenta. In a number of cases in which the 
mother had advanced tuberculosis the organs and 
blood of the fetus (stillborn or dying soon after 
birth), contained very many bacilli, although his- 
tologic lesions had not as yet been produced. 
Warthin and Cowie suggest that the tissues of the 
fetus may possess considerable immunity in such 
cases. Baumgarten is a strong believer in the pos- 
sibility that tubercle bacilli may pass to the fetus 
during pregnancy and, remaining latent in some 
of the tissues (lymph glands) for a long period, 
cause active tuberculosis later in life. Others who 
are less radical still admit that we should consider 
this as a possibility (Warthin and Cowie, Har- 
bitz). 
infection Pulmonary tuberculosis is by far the most com- 
mon form of the disease in man, and without doubt 
this is due to inhalation of the dried and pulver- 
ized sputum of tuberculous patients. Drop infec- 
tion may well occur in the case of those who are in 
intimate contact with the sick. In kissing, direct 
infection from mouth to mouth is a dangerous 
possibility. 

The reason for the inception of pulmonary tu- 
berculosis in the apex in so many cases is not clear- 
ly recognized, although it is often referred to the 
relative immobility of this tissue, which renders 
excretion more difficult and ' affords improper 
aeration. These conditions not only allow the or- 
ganisms to accumulate and to proliferate, but the 
• insufficient oxygenation probably causes a low tis- 



TUBERCULOSIS. 419 

sue resistance. The suggestion which has been 
made that apical tuberculosis i? the result of ex- 
tension of the disease from the cervical glands does 
not correspond with the condition seen in tubercu- 
losis of adults in whom the cervical adenitis is 
commonly wanting. 

The "anatomic tubercle" is a primary infection 
of the skin; lupus vulgaris, it is supposed, may be 
either a primary infection or secondary to tubercu- 
losis in some other organ; ulcerative tuberculosis 
is usually a secondary lesion, often occurring by 
direct extension from tuberculous lymph glands. 
Tuberculosis of the nose is uncommon. Infection 
of the tonsils is not infrequent and probably is a 
common cause of secondary tuberculosis of the cer- 
vical lymph glands. Primary infection of the 
pharynx sometimes occurs and large, coarse granu- 
lations of this surface have been proved in some 
cases to be of a tuberculous nature. Tuberculosis 
of the pharynx and larynx, however, most often 
arises from infection with tuberculous sputum. 

In the process of dust infection of the lungs, and 
also by other means, many organisms lodge on the 
mucous membranes of the nose, mouth, pharynx, 
trachea and larger bronchi, but usually without 
producing a tuberculous infection. On account of 
the movement of the ciliated epithelium, tortuos- 
ity of the nasal channels, excretion of the bacilli 
with mucus, the conditions at these points are not 
favorable for infection. 

Tuberculous ulcers of the esophagus and stom- 
ach are very rare, as is primary tuberculosis of the 
intestines. Secondary tuberculosis of the intes- 
tines usually is caused by the infected sputum 



420 INFECTION AND IMMUNITY. 

which the patient swallows. Primary infection of 
the genital organs may arise from direct contact. 

That tubercle bacilli have often been found on 
the hands and finger nails of the sick as well as on 
those who are intimately associated with them is a 
significant fact in relation to the possibility of in- 
fection by direct contact. 
Metastases. From a given focus tubercle bacilli extend to 
other structures in several ways. On more or less 
theoretical grounds one speaks of "extension by 
growth" of the organism into contiguous tissues. 
The commonest method of extension, however, is 
that of metastasis by way of the lymph channels. 
When bacilli penetrate a surface, with or without 
the formation of a lesion at the point of entrance, 
as in the mouth cavity, intestinal canal, or bron- 
chial surface, they are carried to the lymph glands 
of the region in which the tuberculous process is 
instituted. As in plague, the infection atrium at 
times is indicated by the set of glands which is in- 
volved. In certain localities the secondary invasion 
of other structures takes place directly without the 
intermediate involvement of lymph glands, as in 
tuberculous meningitis caused by extension from 
the middle ear, and tuberculous peritonitis or peri- 
carditis by extension from the pleura. Yery fre- 
quently tuberculosis of the lymph glands and other 
tissues heals spontaneously, as described below. In 
case such healing does not occur, metastases con- 
tinue from one lymph gland to another and to new 
sets of glands until the larger lymph channels are 
reached, as a consequence of which extensive re- 
gional or general tuberculosis results. Accidental 
localization of a focus often causes a wide depart- 
ure from the slow development just described. Not 



TUBERCULOSIS. 421 

infrequently tuberculosis in a lymph gland, which 
is contiguous to a large lymph channel, as the tho- 
racic duct, invades the wall of the latter, the sur- 
face softens from caseation or liquefaction and the 
contents, impregnated with countless bacilli, are 
gradually thrown into the circulation. Miliary 
tuberculosis, first of the lungs and then of other 
tissues, through the arterial circulation, follows 
such an accident. A similar course with variations 
in localization, follows invasion of the walls of 
branches of the pulmonary artery or vein. Eup- 
ture of a focus into a bronchus is followed by re- 
gional or more extensive dissemination of the ba- 
cilli throughout the lungs by respiratory forces. 
A slower eccentric extension is seen, particularly 
in the lungs, in which smaller and larger areas of 
consolidation occur. By means of short lymphatic 
metastases into contiguous territory new foci are 
instituted, which eventually fuse with the original 
lesion. It is suggested and generally believed that 
bacilli may be carried longer or shorter distances 
by wandering phagocytic cells. When tuberculosis 
once involves a surface like that of the pleura, peri- 
toneum, pericardium or pelvis of the kidney, the 
whole surface frequently becomes involved in 
thickly studded miliary tubercles. It is probable 
that a great deal of dissemination is accomplished 
by the movements of the fluids and the surfaces of 
these cavities. In other instances, as in the ure- 
ters, Fallopian tubes and spermatic cords, exten- 
sion seems to occur in the submucous tissue by 
means of the lymphatics. The autopsy often dis- 
closes that tuberculosis which appeared to be "pri- 
mary" in such organs as bones, suprarenal glands, 
and meninges was preceded by an old process in a 



422 INFECTION AND IMMUNITY. 

lymph gland from which metastases occurred to the 
tissues in question. 
The Tubercle Certain anatomic conditions produced in tuber- 

and Other Tis- i • i • i • i n -ii j> i_i 

sue changes, culosis which are associated with recovery irom the 
disease, or the contrary, may be referred to. The 
tubercle, the histologic unit of the tuberculous 
process, is produced as follows, according to the 
interpretations of Baumgarten: When a bacillus 
reaches a lymph gland, for example, it multiplies 
slowly and, partly through its presence as a foreign 
body, but particularly through its toxic secretions, 
injures the surrounding connective tissue and en- 
dothelial cells to a certain degree. Under some 
circumstances, especially in the parenchymatous 
organs and lymph glands, this injury may be so 
great as to cause the death of the adjacent cells 
(focal necrosis). When it is of a lower order the 
connective tissue and endothelial cells respond to 
the stimulus by dividing mitotically and eventu- 
ally accumulate in large numbers within a limited 
area surrounding the micro-organisms. Not only 
the endothelial cells of the lymph spaces, but also 
those of the adjacent blood vessels, take part in 
the proliferation, many of the vessels being obliter- 
ated in consequence. Not infrequently bacilli are 
ingested by the new cells, although the ability of 
the latter to destroy the organisms is not clearly 
established. Metchnikoff says that tubercle bacilli 
may remain intracellular for many months and, 
although not killed, the pathogenicity is decreased 
or destroyed. The new cells are of polygonal shape, 
are fairly rich in cytoplasm, contain large vesicular 
nuclei and are termed "epitheloid" cells. 

Certain of the epitheloid cells, usually those in 
the center of the tubercle, where the bacilli are 



TUBERCULOSIS. 423 

most numerous, undergo atypical proliferation in Giant 
that repeated nuclear division takes place without 
corresponding division of the cytoplasm. This 
process results in the formation of the multinu- 
clear giant cell which is so characteristic of the 
well-developed tubercle, although not distinctive of 
the disease. According to Weigert, the failure of 
complete cell division is due to injury to the cyto- 
plasm (partial necrosis) by the bacteria which the 
cell contains. Metchnikoff and others take a dif- 
ferent view of the formation of giant cells, con- 
sidering that they represent individual epitheloid 
cells which have fused to form a multinuclear 
mass. 

Still more remote from the center of the tuber- Retrogressive 
cle, that is, surrounding the epitheloid cells, wan- 
dering lymphoid and plasmal cells accumulate. 
Certain retrogressive changes, especially necrosis 
and caseation, characterize the further history of 
the tubercle, although these changes do not occur 
equally early nor with equal intensity in all cases. 
Necrosis begins in the center of the lesion, and the 
view is often expressed that the formation of the 
giant cell is the first indication of the retrogressive 
change. Cell degenerations, however, with karyor- 
rhexis may occur before giant cells have formed. 
With the death of the central tissue there occurs 
sooner or later the death of many of the bacilli in 
this portion of the tubercle. The progressive for- 
mation of new tissue continues in the periphery as 
the degenerative changes take place toward the 
center; the tubercle enlarges, both epitheloid and 
the surrounding lymphoid cells increase corre- 
spondingly, and new giant colls form at the periph- 
ery of the necrotic center, only to be included in 



424 



INFECTION AND IMMUNITY. 



Formation of 
Fibrous Tissue. 



Caseation, Cal- 
cification and 
Liquefaction. 



General and 

Secondary 

Disturbances. 



the degenerated area as the latter extends. In 
favorable cases, in which the virulence of the or- 
ganism is low or the resistance of the individual 
strong, the tuberculous area is eventually sur- 
rounded by adult fibrous tissue which in a sense 
accomplishes the isolation of the infected area. 
Without question such a capsule of scar tissue is an 
obstacle to the extension of the tuberculous proc- 
ess, whether it surrounds a nodule in a lymph 
gland, a cold abscess or a tuberculous sinus. 
Further steps in the healing consist of caseation of 
the entire area, its partial or complete substitution 
by connective tissue (tuberculous scar), or partial 
impregnation with lime salts (calcification). Not 
infrequently the caseous portion of a nodule under- 
goes liquefaction, which some have referred to the 
action of proteolytic ferments. The contents of 
such foci finally become sterile. In the event that 
healing of this nature does not occur, the infection 
is transmitted to other organs as described above. 

The temperature, loss of weight, fever, increased 
cardiac action, and arteriosclerosis which are seen 
in tuberculosis indicate that the products of the 
bacillus have a profound effect on the functions of 
the body, and produce great disturbances in meta- 
bolism, although they seem to have no marked se- 
lective action for particular tissues. Many disturb- 
ances are secondary to changes produced in partic- 
ular organs and are not referable to specific ac- 
tion of the toxins, such as those which are conse- 
quent on poor oxygenation in pulmonary tuberculo- 
sis, and the amyloid degeneration which follows 
prolonged suppurative tuberculosis. 

Mixed infection, especially with the streptococ- 
cus, plays a very important part in the course of 



TUBERCULOSIS. 



425 



pulmonary tuberculosis, especially in the caseous 
and cavernous forms. Staphylococci, B. pyocya- 
neuSj various diplococci, the pneumococcus, bacil- 
lus of Friedlander, diphtheria and pseudo-diph- 
theria bacilli, and the influenza bacillus are also 
found as secondary organisms in pulmonary tuber- 
culosis. Some of them invade the surrounding 
healthy tissue, cause lobular consolidations, and in 
this way probably prepare a favorable soil for 
further extension of the tuberculous process. They 
doubtless hasten the liquefaction of caseated tissue. 
a step in the formation of abscesses. The high and 
irregular fever often seen in advanced tuberculosis 
is commonly septic in its cause, and a terminal 
streptococcus septicemia is not infrequent. It is 
evident that mixed infections may complicate at- 
tempts at serum therapy. 

The essential principles in the prevention of 
tuberculosis consist of, first, the early recognition 
of the disease, so that the patient may be properly 
treated and cured, if possible, with the result that 
a new center of contagion is avoided; second, the 
rendering of well-developed cases harmless by suit- 
able isolation and proper disposal of infected ex- 
cretions; third, the disinfection of the rooms, 
clothing, linen and surroundings of tuberculous 
patients. A fourth point, the prohibition of mar- 
riage among the, tuberculous, is one of great con- 
sequence, although we have little ground to hope 
for its realization. A fifth point, not yet fully 
established, is the possibility of universal vaccina- 
tion against the disease. 

The collection of infected sputum in properly 
constructed water-proof paper boxes, which, with 
their contents, should be burned daily, Lb the safesl 



Mixed 
Infections. 



Principles of 
Prophylaxis. 



426 INFECTION AND IMMUNITY. 

Disposal method of disposing of this material, and the most 
effective means of preventing infection of the pa- 
tient's surroundings. Metallic, glass or earthen- 
ware sputum-cups containing 5 per cent, carbolic 
acid are serviceable, but must be subjected to fre- 
quent cleansing. When sputum is collected on a 
handkerchief the latter should be boiled within 
twelve hours and not allowed to dry ; that the hands 
of the patient are likely to be contaminated from 
the handkerchief is evident. In coughing, the 
handkerchief should be held to the mouth to catch 
droplets of sputum and saliva which are expelled. 
The ordinances and rules which prohibit expecto- 
ration in street cars and other public places should 
be enforced. When bacilli are discharged in the 
urine and feces or in the pus of tuberculous ab- 
scesses and sinuses, these secretions should be dis- 
infected by suitable means (chlorid of lime). 
Healthy persons should come in contact with the 
tuberculous as little as possible, and the eating 
utensils of the latter should be used by no one else. 
Disinfection. The floor of a room which is inhabited by a tuber- 
culous person should always be moistened before it 
is swept, in order to avoid stirring up the dust. 
After the death or removal of a patient, the entire 
surface of the room and all its contents should be 
thoroughly disinfected by appropriate means. The 
proper disinfection of the premises which were 
once occupied by a consumptive should be a legal 
requirement, just as similar procedures are de- 
manded in the case of smallpox and some other 
contagious diseases. 

The special hospital in which the indigent tuber- 
culous may be properly cared for and isolated has 



TUBERCULOSIS. 



427 



been a powerful factor in causing the decrease of 
tuberculosis which has been noted in many coun- 
tries. The removal of a patient to such an institu- 
tion means the elimination of an infected focus 
from the community. 

Cold-blooded animals (fish, amphibians, rep- 
tiles), and most birds are not highly susceptible to 
tuberculosis, although special varieties of the ba- 
cillus cause the disease in certain of them under 
natural conditions. When tubercle bacilli are in- 
jected into the circulation of birds, they may re- 
main in the blood and organs for months, produc- 
ing little or no tissue change, although they retain 
their virulence for other animals (guinea-pigs). 
No animal exceeds the guinea-pig in its susceptibil- 
ity to this disease. Goats and sheep are fairly re- 
sistant, and the same is probably true of the horse, 
although its artificial infection is not difficult. 
That different varieties of a species may vary in 
their susceptibility is illustrated by the field mouse, 
which is highly susceptible, and the white mouse, 
which is relatively immune. Although similar 
variations may exist among different races of men, 
they are not readily demonstrated. The high sus- 
ceptibility which appears to exist among certain 
races, as the negro, may be explained in part by un- 
hygienic methods of living, in which safeguards 
against infection are not taken. 

The discovery of healed or healing tuberculous 
foci in 70 to 90 per cent, of all autopsies, in con- 
trast to the 15 to 20 per cent, of deaths from tuber- 
culosis, shows that susceptibility and immunity arc 
subject to marked individual variations. The 
ability of an individual to overcome a tuberculous 
infection is referred in a vague way to an unusual 



Susceptibility, 
and Immunity. 



Racial and 
Individual 
Variations. 



428 INFECTION AND IMMUNITY. 

resistance on his part; his defensive powers are 
said to be strong. Although we remain to a large 
extent in the dark concerning these defensive 
powers, they seem to rest chiefly in the ability of 
the tissues to destroy the bacilli; that is, the re- 
sistance is antibacterial. Many bacilli may be de- 
stroyed by leucocytes or endothelial cells before 
they are able to cause tissue changes. It was stated 
previously that healing in many instances depends 
on isolation of the focus by epithelioid, lymphoid 
and plasma cells, and by connective tissue. On 
general grounds we may assume that a tissue reac- 
tion of this nature takes place with greater vigor 
and rapidity in a strong, healthy person than in 
one of lower vitality. Aside from the question of 
individual resistance, recovery or progressive infec- 
tion may depend on the smaller or larger amount 
of bacilli which gained entrance to the body, as 
well as on their virulence. Experiments show that 
susceptible animals recover from minute doses, 
whereas they succumb to somewhat larger doses of 
bacilli. 
Predisposing Various external influences increase susceptibil- 
in uences. ^ an( ^ resistance. Tuberculosis is to no small de- 
gree a disease of the poor, who so frequently live 
in an undernourished condition, in crowded, dirty 
rooms, with little sunlight and fresh air. The 
disease is more common in the city than in the 
country, where an outdoor life is the rule. Alco- 
holism, diabetes, measles, scarlatina, whooping 
cough often, and influenza not infrequently,, are 
precursors of tuberculosis. Conditions which favor 
anemia, as pulmonary stenosis (rare), predispose 
to pulmonary tuberculosis, whereas insufficiency of 
the left heart, accompanied by congestion of the 



TUBERCULOSIS. 429 

lungs, is not often associated with the disease, al- 
though it has no influence in preventing infection 
in other organs. Tuberculosis is more frequent 
.during the first two or three years of life, when 
children are so commonly confined, than from the 
third to the fifteenth year, when they live in the 
open air so largely. From the fifteenth year to 
middle life or later the disease increases in fre- 
quency because of greater exposure to infection. 
Physicians who are familiar with tuberculosis in 
Scandinavian countries and in America comment 
on the extent to which tuberculosis develops among 
Scandinavians after they come to this country. 

Nothing is commoner than the occurrence of -Hereditary 
several successive cases of phthisis in the members Tendency -" 
of a family, and the expression, heard on all sides, 
that "tuberculosis is in the family/' indicates the 
general belief that a family tendency may be trans- 
mitted from generation to generation. During 
recent years, however, closer analysis of the condi- 
tions has led many to doubt the existence or, at any 
rate, the importance of family tendency or inher- 
ited predisposition, and to refer the frequent oc- 
currence of tuberculosis in a family to the greater 
exposure to infection which is occasioned by close 
contact with a pre-existing case. Cornet, who has 
made a close statistical study of tuberculosis, dis- 
credits entirely the hypothesis of hereditary pre- 
disposition, and Cornet and Meyer refer to the 
"habitus plithisicus" which we are disposed to 
look on as an objective evidence of hereditary ten- 
dency, as a result rather than a cause of pulmonary 
tuberculosis. It is fair to say that the development 
of tuberculosis in several members of a family is 
not pi'ima facie evidence of the existence of a 



430 INFECTION AND IMMUNITY. 

family predisposition for the disease. Where there 
are tubercle bacilli there is likely to be tuberculosis, 
and the occurrence of the infection in one fur- 
nishes the prerequisite, that is, bacilli, for the de-. 
velopment of the disease in other members of the 
family. It is probable that the verdict of family 
tendency has often been pronounced erroneously. 
At the present time, however, we may not be justi- 
fied in considering the subject a closed chapter. 
Concerning It is the commonly accepted opinion that recov- 
immunity, ery from tuberculosis does not confer immunity to 
subsequent attacks. Cornet and Meyer suggest as 
an explanation of this condition that the local le- 
sion is so strictly isolated that a sufficient amount 
of toxin does not escape into the circulation to 
cause a general reaction, hence the formation of an- 
titoxin or other antibodies is impossible. This ex- 
planation seems inadequate, however, when we re- 
member the strong antitoxic immunity which de- 
velops in tetanus and diphtheria in spite of the lo- 
calization 01 the bacteria. The results of artificial 
immunization, in which unlimited amounts of 
toxic ' material or bacilli may be injected without 
the formation of satisfactory antitoxins, seem to 
indicate that the toxic constituents of the tubercle 
bacillus lack the power of causing the formation of 
a strong antitoxin. 

In opposition to the prevailing opinion, certain 
observers find ground for the belief that recovery 
from local tuberculosis of the lymph glands, skin or 
bones, actually does render the patients immune to 
pulmonary consumption (Maragliano and others). 
In early experiments Koch noted that when tuber- 
cle bacilli were injected subcutaneously into 
guinea-pigs which were suffering from general tu- 






TUBERCULOSIS. 431 

berculosis, the subcutaneous inoculation remained 
as a local infection and not infrequently healed 
after sloughing. The general infection would seem 
to have increased local resistance. Although other 
investigators failed to duplicate the observation of 
Koch, this result is said to have suggested to him 
the idea of active immunization as a cure for tu- 
berculosis, a method subsequently practiced by 
treatment with the various tuberculins. 

In the United States, Trudeau and de Schwein- Active 
itz, and in Europe, Koch, Behring, Maragliano 
and Baumgarten, with their followers, have prac- 
ticed assiduously the artificial immunization of 
animals with the tubercle bacillus or various prep- 
arations from the organism, with the hope of pro- 
ducing active immunity to the disease. Some of 
the procedures, especially those of Koch, have been 
transferred to man as curative measures. In addi- 
tion to active immunization of man, Maragliano 
especially has prepared an antituberculosis serum, 
to which he assigns antitoxic and bactericidal 
properties, and which he and others claim to have 
used with good results in the treatment of tuber- 
culosis. Marmorek also prepares an "antitoxic" 
serum. 

It has been shown that active immunization 
may so increase the resistance of various domestic 
animals (guinea-pig, sheep, rabbit, dog, calf, cow, 
etc.), that they withstand doses of bacilli which 
are invariably fatal for control animals. When 
the bacterial cells are used for immunization it is 
customary to begin treatment either with killed 
bacilli, or with living cultures which are naturally 
of low virulence, or the virulence of which has been 
lost by prolonged artificial cultivation. Relatively 



Immunization. 



432 INFECTION AND IMMUNITY. 

avirulent strains as those cultivated from fish, 
turtle or fowls, have been utilized for the first in- 
jections. As immunization progresses one of two 
processes may be followed: either the quantity in- 
jected may be increased gradually, as when killed 
or avirulent bacilli are used, or the immunization 
having been begun with avirulent living cultures 
those of higher virulence may be substituted later. 
In any case immunization is difficult and slow, 
and many animals may be lost from cachexia or 
from tuberculosis which develops from hasty pro- 
gression in dosage. The subcutaneous injection 
of intact cells has the disadvantage that local ab- 
scesses frequently develop, and to avoid this the 
intravenous injection of smaller doses has been 
practiced in some instances. For active immuniza- 
tion the "new tuberculin" of Koch containing all 
the cellular constituents in a finely divided form 
has the advantages that it may be given subcu- 
taneoiisly without abscess formation and is ab- 
sorbed with some rapidity. An animal or person 
immunized with TE is immune to all the constitu- 
ents of the bacillus. The condition produced by 
active immunization is one of increased resistance 
rather than of absolute immunity; large doses of 
bacilli may cause infection. The nature of the 
new resistance is not satisfactorily established. 
Tuberculin Inasmuch as tuberculin is used not only for 
diagnosis but also for curative purposes in man 
(active immunization), and since the principles of 
action are similar in both instances, the use of 
tuberculin may be considered at this point. A 
healthy man is not susceptible to moderate doses, 
but a tuberculous man is even more susceptible 
to the toxin than the tuberculous guinefe-pig. 



in Diagnosis. 



TUBERCULOSIS. 433 

since 0.001 c.c. often causes an intense reaction. 
E. TTeigert classifies the disturbances which tuber- 
culin may produce in the tuberculous as thermal, 
circulator}', respirator}-, digestive, nervous and 
vasomotor, and secretory. Necrosis may be pro- 
duced at the point of injection. In so far as the di- 
agnostic use of tuberculin is concerned, we are in- 
terested chiefly in the thermal disturbances, 
which are accompanied by chills, malaise and 
muscular pains. Following injection of a suitable 
quantity, a period of incubation of from eight to 
fourteen hours follows, and at the end of this time 
the temperature rises progressively for two or 
more hours and may reach a maximum of from 40° 
to 41° C; after remaining at this point for from 
two to six hours, it recedes rapidly. In addition 
to this general reaction, the toxin causes conges- 
tion, redness and swelling at the site of the tuber- 
culous lesions, i. e., the foci become surrounded by 
an inflammatory reaction. This is seen most 
readily in the tubercles of lupus vulgaris, and in 
the lungs declares itself by an increase in rales 
and expectoration, caused by the exudation ac- 
companying the inflammatory reaction. 

For diagnostic purposes the technic of adminis- 
tration is as follows: It must first be assured 
that the patient has no continued fever by noting 
the temperature every two hours for several days. 
One milligram of tuberculin is injected subcu- 
taneously, this amount being obtained by suitable 
dilution of the original solution. If no tempera- 
ture is produced by this amount, 5 or 10 mg. may 
be given in a second injection after an interval of 
two or three days. When the quantity is determined 
which causes a rise in temperature of one-half 



Limitations in 
Diagnostic Use 



434 INFECTION AND IMMUNITY. 

degree C. or more, the dose is to be repeated after 
the temperature produced by the first injection has 
subsided. Two positive reactions should be con- 
sidered necessary for the diagnosis of tuberculo- 
sis. One who, after injection of 10 mg. on two 
different occasions, gives no reaction is to be con- 
sidered free from the disease (Marx). 

Experience has taught certain limitations to the 
of Tuberculin' diagnostic value of tuberculin: 1. The test can 
not be applied to febrile cases inasmuch as the 
pre-existing fever could not be separated from that 
which the tuberculin might produce. 2. Cases of 
advanced tuberculosis frequently fail to give the 
reaction. The tissues of such patients have be- 
come resistant to the poison. 3. It is said that 
tuberculin frequently causes a similar reaction in 
those suffering from leprosy, actinomycosis and 
syphilis. Cornet and Meyer suggest that the 
phenomenon as it occurs in leprosy and actinomy- 
cosis is to be considered in the nature of a "group 
reaction" in view of the close relationship of the 
tubercle bacillus to actinomyces and Bacillus leprce 
It does not always occur in syphilis, and in posi- 
tive cases a latent tuberculosis may be responsible 
for the reaction. By a number of writers the facts 
just stated are taken to indicate that the reaction is 
not of specific character; that it may often be ob- 
tained in the tuberculous by the injection of ap- 
parently indifferent substances as trypsin, peptone 
(albumose), sodium cinnimate and the "mycopro- 
teins" of other bacteria provides additional sup- 
port to this view. On the other hand, since rela- 
tively large amounts of these indifferent sub- 
stances are required to produce the reaction, where- 
as minute amounts of tuberculin suffice, others 



TUBERCULOSIS. 435 

hold that the specificity of the latter substance 
may be maintained. 

Early tuberculosis reacts to tuberculin in the 
most typical manner. On account of the fact that 
latent or healing cases may respond to the test, its 
positive outcome gives no indication of the serious- 
ness of the patient's condition, which is a practical 
question of some importance. 

The fear that tuberculin, in producing an in- Dangers?) 
flammatory reaction around tuberculous areas, Tuberculin. 
may cause a dissemination of the bacilli, has acted 
strongly in preventing the use of the toxin for 
both diagnostic and therapeutic purposes. On a 
priori grounds, such an event would seem to be a 
possibility, for, with the inflammation, the vessels 
surrounding the tubercles become congested, new 
leucocytes accumulate and there is an extravasation 
of fluid. Since during the subsidence of the in- 
flammation a certain number of leucocytes may 
again leave the area and as the extravasated fluid 
returns to the circulation, bacilli may be carried to 
other tissues by them. Contrary to such reasoning, 
however, the observations of Koch and his follow- 
ers in animal experiments and in the diagnostic 
and therapeutic use of tuberculin in man, lead 
them to say that tuberculin when properly ad- 
ministered never causes an aggravation or exten- 
sion of the disease. Similar conclusions were 
reached by Trudeau, Baldwin and Kinghorn in 
animal experiments in which, "as in previous ob- 
servations, a favorable absorptive influence was 
noted on the diseased focus." Bearing in mind 
the limitations mentioned above, and the possibil- 
ity of the reaction being induced by leprosy, acti- 
nomycosis and syphilis ( ?), the statement of Osier 



1 
436 INFECTION AND IMMUNITY. 

may be quoted that "in obscure internal lesions, 
in joint cases and in suspected tuberculosis of the 
kidneys the use of tuberculin gives most valuable 
information" 
Tuberculin The original unfavorable results which were ob- 
tained in the therapeutic administration of tuber- 
culin are referred by Koch, Petruschky and others 
to improper selection of cases. Those in a febrile 
condition and those in whom destruction of tissue 
is advanced are not suited for the treatment, and 
in them little or nothing is to be hoped from the 
administration of tuberculin. Its curative value is 
supposed to depend on the local inflammatory reac- 
tion which it causes around tuberculous foci, and 
perhaps also on the necrosis which Koch claims is 
caused in the tubercles themselves. It must be the 
object during the whole course of treatment to ad- 
minister the toxin in such doses that a moderate 
or minimum local reaction occurs. Larger amounts 
which would cause febrile reactions and eventually 
render the patient resistant to tuberculin and thus 
preclude the local changes are to be avoided. It is 
customary to begin with 1/10 to 1/20 milligram 
and gradually to increase the amount injected. 
If fever is caused by a particular dose, larger 
amounts are not to be given until fever ceases to 
follow this dose. By the time a dosage of 50 milli- 
grams is reached, which may require many months, 
the patient usually has lost the power of reacting 
and the injections are to be interrupted until he 
again becomes sensitive to the toxin (from three 
to six months), after which treatment should be 
resumed. Cure is recognized when the patient has 
lost permanently the power to react, his condition 
then being identical with that of the healthy man. 



TUBERCULOSIS. 437 

Xumerous German writers on the basis of practi- 
cal experience assign an unquestionable curative 
power to tuberculin when administered as de- 
scribed. Its use has not extended widely. 

The principles on which the action of tuberculin 
depend are hypothetical. Marmorek says that the 
fever and local changes are due to a special toxin 
(the true toxin), which the bacillus secretes under 
the stimulation of the tuberculin. Ehrlich sup- 
poses that cells adjacent to the tubercles have been 
injured moderately by the tuberculin which is pro- 
duced in situ, and that as a consequence of this 
injury such cells are particularly susceptible to the 
additional tuberculin which is injected, and react 
to the stimulus by proliferation (Marx). In ac- 
cordance with this conception the fever also in 
some obscure way is related to the local reaction. 
Investigations are needed to clear up this point. 

In active immunization with TK, in which the Treatment with 
solid constituents of the bacilli are injected rather Tubercuiilf.^' 
than the toxic tuberculin, the cure is supposed to 
depend on the development of immune bodies 
rather than on local tissue changes. Koch pub- 
lished favorable results from its use, but reports 
from other sources were less satisfactory. Koch's 
Neutuberculln (Bazillenemulsion) is used in a 
similar manner. Koch proposes to use the agglu- 
tinating power of the patient's serum as an index 
of the immunity caused by the injection. The for- 
mation of agglutinins perhaps indicates in a gen- 
eral way the ability of the patient to form anti- 
bodies, but from the well-known fact that the ag- 
glutinating power does not go hand in hand with 
the protective power of serum in relation to many 
infections, this method of estimating the degree 



438 INFECTION AND IMMUNITY. 

of immunity does not rest on a good basis. The 
agglutination reaction is carried on with the emul- 
sion which is used for immunization. Treatment 
in man is begun by the injection of 0.0025 mg. of 
solid substance and the amount is increased rap- 
idly every day or two until a reaction occurs with 
a temperature of from 1.5° to 2° C. After a pause 
of a week the injections are begun again and event- 
ually a dose of 20 mg. may be given. During 
treatment the agglutinating power of the patienf s 
serum is tested frequently, and if it is not suffi- 
ciently high intravenous injection of the fluid por- 
tion of the emulsion may be practiced. The agglu- 
tinating power may go as high as from 1 to 25 to 
1 to 150, rarely 1 to 200 or 300. 

With both TE and the last preparation animals 
may be successfully immunized against tubercu- 
losis. 
Serum of Maragliano publishes the following conclusions. 
Maragfiano. «^ that it - g p 0ss i D i e to produce a specific (serum) 

therapy for tuberculosis; 2, that it is possible to 
immunize the animal organism against tuberculo- 
sis as is done in other infectious diseases, and that 
there is good reason for hope for an antitubercu- 
losis vaccination for man." He recognizes bacteri- 
cidal, antitoxic and agglutinating properties of the 
serum as normal defensive powers of the body, and 
says that these powers are increased as the result 
of immunization. The bactericidal power of the 
serum is determined by its ability to inhibit the 
growth of cultures of the tubercle bacillus; its 
antitoxic power by its ability to neutralize a test 
poison which is obtained from cultures by macerat- 
ing them in hot water; and its agglutinating 
power is tested with the homogeneous cultures of 



TUBEBCULOSIS. 439 

Courmont and Aiioing. For the immunization of 
animals a soluble toxin prepared by the nitration 
of young cultures, and also the intracellular toxins 
which are extracted by water from killed virulent 
bacilli, are injected. By using both substances, 
antitoxic and other antibodies are said to be 
formed. 

The unusual claim is made by Maragliano that 
his antituberculosis serum is effective in the treat- 
ment of human tuberculosis not only because of its 
own properties, but because it causes the tissues to 
form additional antibodies. It is difficult to take 
the latter claim seriously, since it is not in accord 
with the laws of anti-body formation as we under- 
stand them at the present time. However, favor- 
able reports of the value of the serum have been 
published principally from Italian sources. It is 
claimed that the serum manifests its curative pow- 
ers and causes an increase in specific antibodies 
when given per os. 

Maragliano also advocates a method of mixed Mixed immun- 
active and passive immunization in man, in which vacdnatTon. 
a cubic centimeter of serum is given subcuta- 
neously every second day for twenty days; for a 
second period the same quantity of serum is given, 
but supplemented by increasing amounts of the 
toxic extract of bacilli ; and for a third period the 
toxic extract is injected in increasing doses during 
from three to four months. 

The same authority thinks it may be possible to 
vaccinate against tuberculosis by a single subcuta- 
neous injection of a vaccine (killed bacilli?). He 
states that in both man and animals antibodies are 
formed in the serum following the vaccination, and 
that in animals their resistance to infections with 



Marmorek. 



440 INFECTION AND IMMUNITY. 

living bacilli is increased. Marmorek asserts that 
killed tubercle bacilli which have been treated with 
his antitoxic serum are readily absorbed from the 
subcutaneous tissue, and proposes the use of such 
bacilli as a vaccine. 
Serum of As stated above, Marmorek discredits tuberculin 
as the specific toxin of the bacillus. His "true* 7 
toxin is prepared by growing young and virulent 
bacilli ("primitive" bacilli) in a medium which 
contains leucotoxic serum, liver extract, glycerin 
and bouillon. The leucotoxic serum is prepared 
by immunizing calves with the leucocytes of 
guinea-pigs. Theoretical considerations which we 
need not detail suggested the use of this medium. 
The cultures are filtered after a few days of growth 
and the formation of tuberculin is avoided as much 
as possible. The immunization of horses with this 
filtered toxin yields the antitoxic serum of Mar- 
morek. Conflicting reports concerning its value 
are published from French sources. Schwartz an- 
nounces the complete cure of a case of tuberculosis 
of the larynx, and another of virulent tuberculosis 
of the conjunctiva and cornea by the exclusive use 
of Marmorek's serum. 
immunization Both Maragliano and Behring affirm that the 
immunizing substances are excreted in the milk of 
cows which have been strongly immunized against 
tuberculosis, and both have suggested that the use 
of such milk by infants may render them more re- 
sistant to tuberculosis. 

The agglutination reaction has been suggested 
by Courmont and Arloing and others as a means of 
diagnosis in tuberculosis. Others who criticise this 
idea affirm that agglutinins are not developed suf- 
ficiently in tuberculosis to render the test of 



by Milk. 



TUBERCULOSIS. 441 

value, and that the serum of normal man may be 
as highly agglutinating as that of the tuberculous. 
In view of the fact that the tubercle bacillus grow? 
in coherent masses in ordinary cultures special 
manipulations are necessary to render it suitable 
for the agglutination reaction. Courmont and Ar- 
loing prepare a homogeneous culture by first grow- 
ing the organism on a certain potato medium and 
then in glycerin bouillon, which is frequently 
shaken. The cells are said to be well isolated after 
this procedure. Koch uses his emulsion of pow- 
dered bacilli for the test. The serum of man or 
animals as a result of immunization may reach an 
agglutinating power of 1 to 2,000 exceptionally 
(Maragliano). 

APPENDIX. 

TUBERCULOSIS AND PSEUDOTUBERCULOSIS IN ANIMALS. 

Certain differences between the bacilli of human and Bovine 
bovine tuberculosis were mentioned in the preceding Tuberculosis. 
section. In cattle the disease shows a characteristic 
tendency to remain localized in one organ or group of 
organs over a long period. It is a nodular disease as in 
man, but differs from human tuberculosis in that no- 
dules often grow to large size, may be imbedded in and 
sharply differentiated from surrounding healthy tissue, 
and not infrequently involve serous surfaces, forming 
large masses of firm sessile or pedunculated tumors. 
The nodules frequently are fibrous from the beginning, 
undergo early and extensive calcification and rarely 
soften. We are not to understand, however, that miliary 
tuberculosis does not occur in cattle. Although the 
process in the lungs is usually of a fibrous and large 
nodular nature, rapid dissemination with formation of 
many miliary tubercles may cause the picture of acute 
tuberculous consolidation in a certain number of cases. 
According to the statistics of Ostertag, based on 43,000 
cases of bovine tuberculosis, localization is as follows: 
Lungs, 75 per cent.; pleura and peritoneum, 50 per 
cent. ; peribronchial glands, 00 per cent. ; spleen, 40 per 
cent. In more or less generalized cases the lungs are in- 
volved in 100 per cent, of the cases; serous membranes, 



442 INFECTION AND IMMUNITY. 

90 per cent.; liver, 85 per cent.; digestive tract, 60 per 
cent.; spleen, 50 per cent.; kidneys, 30 per cent.; mouth 
cavity, 5 per cent. In cows the uterus, in general infec- 
tion, is involved in 65 per cent, of the cases, the udders 
in from 5 to 10 per cent., and the ovaries in 5 per cent. 
It seems that the lungs are the most common infection 
atrium, and transmission probably is accomplished chief- 
ly through the secretions of the respiratory passages. 
In the udders the process may at first be one of miliary 
tuberculosis, but a large amount of fibrous tissue forms 
in time, many acini are transformed into retention cysts, 
in which tubercle bacilli, free or intracellular, may be 
present in large numbers. 

Aside from anatomic changes and clinical symptoms, 
diagnosis depends on the tuberculin reaction, and, in 
relation to the udder, the demonstration of bacilli in the 
milk by staining methods or inoculation into guinea- 
pigs. 

The tuberculin reaction in cattle is similar to that in 
man and is subject to the same general limitations, but 
is used extensively with the most satisfactory results. 
The complete elimination of tuberculosis from herds of 
cattle is possible, by using tuberculin as a diagnostic 
test, the slaughtering of infected animals, and the dis- 
infection of stalls. 

Tuberculosis among sheep and goats is rare. It occurs 
occasionally in the horse, hog and dog, and with more 
frequency in the cat. 
Avian ^ form of tuberculosis is very common in the chicken, 
Tuberculosis, and attacks also the pheasant, dove and turkey. The 
duck and goose are exempt from it. Although the or- 
ganism resembles that of human tuberculosis in size, 
staining properties and other general characteristics, 
differentiation is accomplished by means of the follow- 
ing points: 1. The avian bacillus shows a greater tend- 
ency to pleomorphinism as shown by club-shaped forms, 
unstained vacuoles, "spore-like" bodies, and branching 
threads. 2. It has a greater affinity for aqueous anilin 
dyes. 3. Growth takes place in artificial media more 
rapidly and on solid surfaces is characterized by its 
moist appearance and mucus-like consistence in contrast 
to the dry, warty, brittle growth of the human bacillus. 
4. The optimum temperature for growth (from 40° to 45° 
C.) is several degrees higher than that of the mamma- 
lian organism. 5. Its pathogenicity for guinea-pigs is 
less and for rabbits greater than that of the human and 
bovine bacilli. Their difference in pathogenicity is 
further shown by the difficulty which is met in trying to 



PSEUDOTUBERCULOSIS. 



443 



infect fowls with the human bacillus. By varying the 
conditions of cultivation and by animal passage the two 
may be made to resemble each other very closely, al- 
though the permanent transformation of the human into 
the avian, or vice versa, has not been accomplished. 

The disease attacks especially the intestines, mesen- 
tery and liver, in w T hich are found hard, yellowish-white 
nodules, often rich in lime salts, and varying in size 
from that of a pea to that of a walnut. These condi- 
tions suggest the intestines as the infection atrium. The 
foci are rich in bacilli and histologically show the es- 
sential characteristics of tuberculosis. 

"Bacillus tuberculosis piscium" is the name given to 
an acid-fast organism resembling the tubercle bacillus 
which was cultivated from an inflammatory tumor in 
the abdominal wall of a carp. It grows well at low tem- 
peratures, the optimum being 25° C, is found in large 
numbers in the lesions within giant cells, and is dis- 
tinctly pathogenic for frogs. Certain authors state that 
the human bacillus when inoculated into the frog under- 
goes changes in its cultural and pathogenic characteris- 
tics, eventually resembling the organism cultivated from 
fish. 

Similar bacilli have been cultivated from a form of 
tuberculosis in the turtle (Friedman), and Blindsch- 
leiche — blind worm ( Moeller ) . 

OTHER ORGANISMS RESEMBLING THE TUBERCLE BACILLUS. 

Certain other organisms of low pathogenicity resemble 
the tubercle bacillus in their acid-fast properties, their 
ability to grow in the form of branching threads, and to 
produce tubercular or nodular infections of a local na- 
ture in animals. They may be placed in a group which 
includes the tubercle bacillus. 

C. Fraenkel, also Neufeld, recognize in smegna two 
acid-fast bacilli, calling one "tuberculoid" because of its 
morphologic resemblance to the tubercle bacillus, and the 
other "diphtheroid" since it shows the pleomorphism of 
the diphtheria bacillus. One of these organisms may be 
identical with the "syphilis bacillus" (?) of Lustgarten. 
Smegma bacilli are most numerous beneath the prepuce 
in man and about the clitoris and vulva in women. 
Their chief significance lies in the danger that they may 
be mistaken for tubercle bacilli in suspected cases of 
genitourinary tuberculosis. Smegma bacilli may readily 
enter the urethra in women and be carried into the blad- 
der during catheterization or cystoscopic examination. 
In man the danger of bacteriologic error may be elimin- 



Tuberculosis 
of Fish, Etc. 



Smegma' Bacil- 
lus and the Ba- 
cillus of Lust- 
garten. 



Bacilli from 



444 INFECTION AND IMMUNITY. 

ated largely by cleansing the glans and carefully irrigat- 
ing the urethra. Urine which is then passed is not likely 
to contain smegma bacilli (Young and Churchman). 

"Milk bacilli" and "butter bacilli" are acid-fast or- 
vfilk'i ! Butter ganisms resembling the tubercle bacillus morphologi- 
and Grass, cally. In injecting milk into guinea-pigs as a test for 
tuberculous contamination, Petri occasionally noted, as 
a consequence, a thick membranous growth which en- 
cased the liver and spleen and bound the coils of intes- 
tines together. The omentum was thickened, and this 
structure and the mesenteric lymph glands contained 
nodules. In pure culture the organism is pathogenic for 
guinea-pigs only when given in large doses, and may kill 
the animals in several weeks with the anatomic changes 
noted above. Its virulence is increased by the simul- 
taneous injection of butter. It is not pathogenic for 
man (Herbert). 

Moeller cultivated organisms resembling the tubercle 
bacillus from timothy (timothy bacillus), from manure, 
and a third (grass bacillus II) from the dust of a 
manger. The last is marked with great pleomorphism, 
thread formation and motility in young cultures. 

The leprosy bacillus and the B. of Lustgarten which 
resemble the tubercle bacillus will be considered later. 

PSEUDOTUBERCULOSIS IN ANIMALS. 

Although some of the organisms described above are 
often called pseudotubercle bacilli, the term pseudo- 
tuberculosis is now applied somewhat specifically to a 
nodular disease occurring in rats, mice and sheep (and 
perhaps in other domesticated animals ) , and in which 
organisms differing from the tubercle bacillus in stain- 
ing and culture properties, morphology and pathogenic- 
ity, are found. The clinical course and anatomic 
changes are similar in the three animals mentioned, al- 
though the organisms are different. The lymph glands 
near the infection atrium become enlarged chiefly by a 
cellular infiltrate rather than extensive proliferation of 
fibrous tissue. The nodules undergo a soft caseation 
very early and rarely show calcification. The infection 
finds its way to other sets of lymph glands and may be- 
come more or less generalized with the formation of 
smaller and larger sized nodules. 
Rats and Pseudotuberculosis of rodents, occurring spontaneous- 
Mice, jy j n rats, guinea-pigs, rabbits and cats, is caused by an 
organism of considerable pathogenicity, and may occur 
in epidemic form in laboratory animals. Chickens also 
may contract the disease. Intraperitoneal inoculations 



LEPROSY. 445 

in guinea-pigs are fatal in a few days. Spontaneous in- 
fection takes place through the intestinal tract, and re- 
gional organs show the principal changes. The liver and 
spleen contain many nodules which may be as large as 
a hazelnut, and which are frequently caseated in the cen- 
ter. The organism is called Bacillus pseudotuberculosis 
rodentium or Streptobacillus pseudotuberculosis dor. 

The disease in mice is caused by a diphtheria-like or- 
ganism called Bacillus pseudotuberculosis murium and 
is pathogenic especially for the gray mouse. 

A similar infection in sheep is of more importance and Sheep. 
occurs with some frequency. It is called pseudotubercu- 
losis ovis, and the bacillus has a corresponding name. 
The organism is supposed to gain entrance through 
wounds in the feet and legs, following which the adja- 
cent lymph glands become involved, and the infection 
may be transferred to the lungs and other organs 
through the lymphatic circulation. The lesions are 
nodular, of varying size, usually surrounded by a fibrous 
capsule, and are either semipurulent Or undergo early 
caseation. They may be found in all the visceral or- 
gans. 

An organism resembling that cultivated from the 
sheep has occasionally been found in nodular conditions 
in cattle. 

II. LEPROSY. 

Leprosy existed in Egypt in prehistoric times course of 
and extended to another land only when inter- Extens,on - 
course was established between the two countries. 
It reached Greece at about 345 B. C, Italy in the 
first century before Christ, and from the latter 
country extended to Germany, France and Spain. 
Crusaders returning from the Orient also brought 
back the disease in later times and eventually all 
Europe was infected. Leprosy is known to have 
existed in Great Britain in the tenth century, and 
from that country it was carried to Iceland and 
Greenland. From Germany it extended to the 
Scandinavian countries, and from the latter to 
Finland and Eussia. It also reached Eussia from 
the South and East, and in the South it was at 



446 INFECTION AND IMMUNITY. 

one time called the Crimean disease. The West 
Indies and South America probably were infected 
from Spain, and through these channels the disease 
was carried to the southern states. The leprosy of 
the western states seems to have been imported by 
Norwegian immigrants chiefly. In 1902 the 
United States leprosy commission found 278 cases 
in this country. One hundred and eighty-six of 
these individuals probably contracted the disease 
in this country, 120 were born in foreign coun- 
tries and 145 were native born. The disease also 
extended around the globe in the opposite direc- 
tion,' reaching China, Japan and the East Indian 
islands from India. The Sandwich Islands be- 
came infected in the nineteenth century. 

The contagiousness of the disease appears to 
have been recognized at a very early period. In 
636 A. D. leprosy houses were instituted in Italy 
and other countries, and the practice of segregat- 
ing lepers soon, became general. The hospitals 
were called Lazarus houses in middle Europe and 
St. George houses in Scandinavian countries. 
Pipin and Charles the Great declared marriage be- 
tween lepers illegal. The rapid disappearance of 
leprosy in middle Europe during the sixteenth 
century is ascribed largely to the segregation of 
the patients. 
Bacillus of In 1872 Hansen announced that small rods, 
Leprosy. some times intracellular and sometimes free, were 
to be found constantly in teased preparations of 
leprous tissue. These rods, leprosy bacilli, are 
now universally recognized as the cause of the 
disease, and in 1879 they were stained by Neisser 
and a year later by Hansen. The organism i? non- 



LEPROSY. 447 

motile, has about the dimensions of the tubercle 
bacillus, the same staining reactions, and fre- 
quently shows a beaded appearance (degeneration 
forms (?) ). It is said to take up dyes more readily 
than the tubercle bacillus, but the difference is not 
so great as to be distinctive. It stains by Gram's 
method. 

Success in cultivating the bacillus has been re- 
ported a number of times, but the researches of 
others have failed to confirm these successes. Up 
to the present time it is probable that the organism 
has not been made to grow in artificial media. The 
resemblance of the bacillus to other acid-fast organ- 
isms, which are not .pathogenic for animals, and 
the non-susceptibility of experiment animals to 
leprosy, are conditions which render very difficult 
the identification of a culture as that of the leprosy 
bacillus. Xicolli is said to have produced leprous 
nodules in monkeys by inoculating them with dis- 
eased tissue. 

So far as known the organism has no natural 
existence outside the human body, and it is dis- 
seminated only by the secretions of the diseased. 
It is discharged chiefly through the secretions of 
the nose and the upper respiratory passages, the 
surfaces of which are so commonly the seat of lep- 
rous ulcers, and also through ulcerating lesions of 
the skin. Expectoration, sneezing and coughing 
have approximately the same significance for the 
dissemination of leprosy bacilli as of tubercle ba- 
cilli. However, the organisms which are found in 
the sputum and nasal secretions appear to be 
largely degenerated, a condition which may lessee 
the infectiousness of these substances. 



Dissemination. 



448 INFECTION AND IMMUNITY. 

Transmission. The infectiousness of the leprosy bacillus is of a 
low character. "Epidemiologic experience teaches 
that infection occurs only through intimate and 
prolonged association with the diseased, in which 
doubtless uncleanliness plays a very important 
role" (Gotschlich). A leprous husband eventually 
infects his wife, and the children of lepers com- 
monly develop the disease early in life. The high 
percentage of leprosy which is noted among the 
laundresses of infected localities indicates that the 
disease may also be transmitted by indirect contact. 
Gotschlich throws some doubt on the importance 
of dust infection since so many of the bacilli found 
in sputum appear to be degenerated. Nothing is 
known of the resistance and viability of the organ- 
ism outside the body. 

Inf Atrial ^ n acc °unt of the early appearance and almost 
constant occurrence of leprous lesions in the nasal 
passages Strieker believes that the latter constitute 
the chief infection atrium; of this Hansen is not 
positive. Nasal ulcers may be present in latent 
or apparently healed cases. Kolle cites a case show- 
ing extensive involvement of the spleen and liver 
in which the intestinal tract was considered the in- 
fection atrium. In some instances in which the 
disease is first noted in the feet, the organisms 
are supposed to gain entrance with infected soil 
through abrasions in the skin. According to Cor- 
nil and Babes, infection may take place through 
the hair follicles and sebaceous glands. The theory 
of Jonathan Hutchinson that leprosy may be con- 
tracted through eating diseased fish, or that the lat- 
ter in some way may render individuals susceptible 
to infection is not now credited. Hereditary 
acquisition of the disease is of doubtful occur- 



LEPROSY. 449 

rence, although the bacilli have been found in ova 
(Babes) and commonly are present in enormous 
numbers in the testicles. Hansen states, however, 
that he has never found them in the female gen- 
erative organs. 

The presence of large masses of bacilli in leprous {j^f,*'™ of 
tissues is a characteristic of the disease. To a large 
extent they are intracellular and they are often 
grouped in such a way as to resemble bundles of 
cigars. Hansen believes that the bacillus is essen- 
tially an intracellular parasite, and that it becomes 
extracellular only as a result of degeneration and 
disintegration of infected cells. Unna, on the 
other hand, considers their location in lymph 
spaces as most characteristic. They appear to be 
carried to distant parts through the lymphatics. 
Certain large vacuolated cells, the lepra cells of 
Yirchow, the gldbi of Hansen, which are filled to 
bursting with the leprosy bacilli, are characteristic 
of the disease. ITnna and others consider these 
bodies as zooglear masses rather than as intracel- 
lular accumulations, and Kanthack interprets them 
as bacillary thrombi in the lymphatic vessels. The 
nodules, or lepromas, consist of granulation tissue, 
containing many round and epithelioid cells, lepra 
cells and occasional multinuclear giant cells. In 
cutaneous macules columns of round cells surround 
the blood vessels, there is some proliferation of 
epithelioid cells, but relatively few bacilli. The 
bacilli are most numerous in the nodular lesions. 
They are found in the Glissonian tissue of the liver, 
in the pulp and follicles of the spleen, in the glom- 
eruli and interstitial tissue of the kidneys when 
these organs are involved, in the nerves in both 
the nodular and maculoanesthetic forms of the 



450 



INFECTION AND IMMUNITY. 



disease, and in the vascular endothelium. They 
have been demonstrated often in the ganglionic 
cells of the posterior root ganglia. Their occur- 
rence in these cells leads Metchnikoff to say that 
the latter have phagocytic properties. 
Endotoxin (?) I n view of the chronic course of leprosy and the 
absence of signs of intoxication over considerable 
periods, it seems probable that the bacillus secretes 
little or no soluble toxin. From time to time, how- 
ever, patients with tubercular leprosy develop fever, 
which may persist for weeks or months and event- 
ually terminate in death. During such attacks 
the nodules not infrequently enlarge, become soft 
and later disappear. Lie conceives that such 
periods represent massive infection of the blood 
with the bacilli, and that at this time the latter 
undergo extensive disintegration and liberate en- 
docellular toxins to which the toxic phenomena are 
due. It is a remarkable fact that intercurrent in- 
fections, as measles and smallpox, and the adminis- 
tration of potassium iodid, cause a similar enlarge- 
ment, softening and final disappearance of leprous 
nodules, accompanied by marked degenerative 
changes in the bacilli. Hansen is of the opinion 
that the fever induced by these conditions has an 
actual curative effect, although its influence is not 
readily analyzed. He quotes the opinion of Dan- 
ielssen that potassium iodid may be used to deter- 
mine the cure of leprosy, which would be indicated 
by absence of a febrile reaction. 

General confidence is not felt in the "leprolin" 
which Eost prepared from his cultures of the lep- 
rosy bacillus (?). His cultures are said to have 
been mixtures of micro-organisms. 

Because of the failure to cultivate the leprosy 



Susceptibility 
and Means 
of Defense. 



LEPROSY. 451 

bacillus, experimental work with the serum and 
cells of man and animals, by which conclusions 
as to the defensive powers of the body might be 
drawn, can not be carried out. It seems probable 
that all men are susceptible to leprosy under the 
proper conditions. Sauton states that children of 
from 4 to 5 years are particularly liable to infec- 
tion. Other conditions which may increase sus- 
ceptibility are of a conjectural nature. It is pos- 
sible that leprosy' predisposes to tuberculous infec- 
tion (?). 

The condition in leprosy s'eems to be that of an 
organism of low virulence against which the body 
possesses no decisive protective agency. The reac- 
tions for the most part are of a local nature, involv- 
ing the proliferation of connective tissue and blood 
vessels, and the accumulation of lymphocytes. That 
phagocytosis by macrophages (lymphocytes, con- 
nective tissue, endothelial and ganglionic cells) is 
a factor which antagonizes the proliferation of the 
bacilli is suggested by the large number of bacilli 
which are found in these cells. 

The principles of prophylaxis may be illustrated Prophylaxis. 
by citing the practices in Norway. Originally all 
lepers were confined to institutions. At the present 
time, however, only indigent lepers and those who 
can not be suitably cared for at home are required 
to enter an asylum, where they live under the best 
hygienic conditions. Other patients are allowed to 
remain at home, with the understanding that they 
sleep alone and, if possible, have separate rooms, 
that their clothing, linen and eating utensils be 
used by no one else, and that proper precautions 
be taken in the washing of linen. Dressings and 
bandages must be burned. Under these regulations 



the Disease. 



452 INFECTION AND IMMUNITY. 

the number of lepers in Norway has decreased from 
2,870 in 1856 to 577 in 1900. Banishment to the 
Island of Molokai is practiced in the Sandwich Is- 
lands. Segregation of lepers should be brought 
about in this country. 

Carasquilla attempted the production of an anti- 
leprosy serum by immunizing horses with the blood 
of leprous patients. Although a few favorable re- 
ports concerning its effects appeared it has not 
proved of value in the hands of others. 

III. GLANDERS (FARCY). 

Occurrence of Under natural conditions the horse is the chief 
sufferer from glanders or farcy, the former name 
being applied to the disease as it occurs in the nose, 
the latter when in the skin. These names are relics 
of the time when the two forms of the disease were 
not recognized as having a common etiology. In 
either locality the disease may be acute or chronic, 
and in the horse about 90 per cent, of the cases 
are chronic. The ass is occasionally infected, and 
in this animal, as well as in man, an acute general 
infection (bacillemia) frequently develops, in ad- 
dition to the cutaneous and nasal lesions which 
characterize the disease. Fortunately, glanders in 
man is rare. Cows and rats are immune, or nearly 
so ; the sheep, goat and dog have fairly high resis- 
tance, although they may be infected artificially; 
the dog and rabbit are moderately susceptible, and 
for the guinea-pig and members of the cat family 
(tiger, lion and leopard), the bacillus is very vir- 
ulent. Infection of the last named animals has 
been noted in menageries as the result of feeding 
them with the meat of a horse which had died of 
glanders. The acute infection usually is fatal, and 



GLANDERS. 



453 



complete recovery from the chronic form of the dis- 
ease is infrequent. Something less than 50 per 
cent, of the chronic infections in man terminate 
in recovery. 

The specific microbe, Bacillus mallei, discovered 
in 1882 by Loefner and Schiitz, is an aerobic or- 
ganism which has approximately the morphology 
and size of the tubercle bacillus, but lacks the acid- 
fast property of the latter. It stains with anilin 
dyes, especially carbol fuchsin, but not by Gram's 
method. With weak staining it shows a granular 
structure. It grows well on ordinary culture media, 
showing a characteristic appearance on potato. In 
unfavorable media it may produce threads, while 
under more favorable conditions coccus-like forms 
are seen. Marked involution forms occur on media 
containing 3 per cent, of sodium chlorid 
(Wherry). The optimum temperature for growth 
is from "30° to 40° C. 

The bacillus is only moderately susceptible to 
sunlight, by which it is killed in about twenty-four 
hours. It withstands freezing, lives for two or 
three weeks in a dried condition at room tempera- 
ture, and is killed by a temperature of from 56° to 
60° C. in from ten minutes to one and one-half 
hours, depending on the amount and character of 
the medium in which it lies. Its resistance to the 
ordinary disinfectants (corrosive sublimate, car- 
bolic acid, etc.), is not high. Milk of lime and 
solutions of calcium chlorid are suitable for the dis- 
infection of stalls. In culture media the organism 
secretes no soluble toxin, but it contains an endo- 
toxin which probably is one of the constituents in 
the various preparations of mallein. 

The method bv which the mallein of Eoux and 



Baciilus 
Mallei. 



Resistance and 
Endotoxin. 



454 . INFECTION AND IMMUNITY. 

Preparation Nocard is prepared is identical with that used in 
the preparation of the old tuberculin. A virulent 
strain of the glanders bacillus is allowed to grow 
for some time (from two weeks to two or three 
months) in bouillon which contains from 4 to 5 
per cent, of glycerin, the culture is then sterilized 
by heat and the bacteria removed by nitration. 
The toxin is not destroyed by high temperature. 
Other preparations, also called mallein, are made 
by extracting ground-up bacilli with a solution of 
glycerin and~ water (Helman, Kalning), or with 
water alone (Kalning and others) ; by killing a 
liquid culture of the bacillus (Bromberg) ; or by 
precipitating bouillon filtrates with absolute alco- 
hol (de Schweinitz and Kilbourne), or with am- 
monium sulphate or magnesium sulphate. The 
dry powders "morvin" and "dried mallein" are 
prepared by one or another of these precipitation 
methods. 
Distribution Glanders bacilli are found only in the tissues 
infection Atria, and secretions of diseased animals, and the nasal 
discharges of the latter are the chief means of con- 
taminating feed, water and stables through which 
the disease usually is carried to other animals. 
The glanders bacillus does not readily penetrate 
the intact skin and mucous membranes, although 
occasionally it may gain entrance through the hair 
follicles or sweat ducts. In the presence of even 
slight defects in these surfaces, as those caused in 
the mouth or nostrils of horses by hay or other 
food, infection readily occurs. According to No- 
card, invasion takes place commonly through the 
gastrointestinal tract following the ingestion of in- 
fected feed or water. Although involvement of the 
intestines and adjacent tissues frequently results. 



GLANDERS. 455 

the organisms may become generalized, causing the 
disease in the nose, skin or other organs, without 
the establishment of foci in the intestines. 

In man infection occurs chiefly through abra- 
sions in the skin, and perhaps also through the 
nose, to which the bacilli have been carried by 
soiled fingers or other means. Several cases of 
acute glanders, ending fatally, have occurred in 
laboratory workers as the result of accidental in- 
oculation. There appears to be little danger to 
man in eating the meat of horses in which the dis- 
ease was localized, provided the meat has been well 
cooked. Such meat was fed to soldiers in one in- 
stance with no ill results. 

Variations in the course of the disease and in the Tissue 
intensity of the pathologic changes in different 
cases probably depend on variations in the resist- 
ance of the host and in the virulence of the para- 
site. In acute general infections in man, follow- 
ing an incubation period of from two to five days, 
during which the point of inoculation becomes vio- 
lently inflamed, a severe febrile condition develops, 
which is accompanied by* general pains, swollen 
joints, a macular eruption, and often muscular and 
subcutaneous abscesses. In a short time nodules 
and indurated cords, made up of a leucocytic exu- 
date, edematous fluid and proliferating connective 
tissue cells, form in the subcutaneous lymphatic 
channels, and mark the progress of the infection 
toward the lymph glands. The nodules, and also 
the cords, commonly undergo softening, and ab- 
scesses fori li and rupture through the skin. Xod- 
ules similar to those in the skin develop in various 
organs of the body; in the nose they break down 
and constitute ulcers. In chronic infections the 



Protective 



456 INFECTION AND IMMUNITY. 

lesions are of the same nature, although they evolve 
more slowly and tend to remain limited to particu- 
lar regions. Nasal, pharyngeal, tracheal or pulmon- 
ary glanders are forms of the disease which are en- 
countered in the horse. Connective tissue develop- 
ment is more marked in chronic than in acute 
glanders, although the peculiar liquefaction, sup- 
puration and ulceration of the lesions occur in the 
former as well as in the latter. Moderate leucocy- 
tosis is found in the blood (12000-14000). 

The nature of the pathologic changes found in 
glanders, the frequent chronic and the progressive 
course of the disease, and the fact that infection 
does not confer distinct immunity, are conditions 
which ally glanders very closely to tuberculosis, 
pseudo-tuberculosis and leprosy. The essential 
lesion is the "infectious granuloma," and it is prob- 
able that the new connective tissue which is formed 
is to no small extent a factor in limiting the exten- 
sion of the infection. Nodules of glanders fre- 
quently are isolated by the surrounding reaction, 
the centers caseate and the contents eventually are 
discharged through the skin; cicatrization and 
healing in many lesions follow evacuation. Phago- 
cytosis of the bacilli by the epithelioid cells and leu- 
cocytes in the nodules is said to be rather extensive. 
According to Nocard, there is no such thing as an 
acquired immunity to glanders; chronic glanders 
may at any time become acute. The cause of the 
natural immunity of cattle and some other animals 
seems not to have been determined. 
serum Therapy Treatment of glanders with immune serums has 
not been successful. Such treatment has been at- 
tempted with serum prepared by immunization 
with mallein (Semmer), and with the serum of 



and Use of 
Mallein. 



GLAXDERS. 457 

diseased animals (Hell and Toeper). The value 
of mallein in the diagnosis of glanders or farcy is 
similar to that of tuberculin in tuberculosis. Al- 
though it causes a rise in the temperature of nor- 
mal animals when given in considerable doses, the 
reaction produced in infected animals is so much 
more intense, and occurs with such smaller doses, 
that it is generally considered as specific in nature. 
Some doubt, however, has been thrown on the spe- 
cificity of the reaction from the facts reported -by 
various observers that toxic substances from other 
organisms, as tuberculin and preparations from 
the pneumobacillus of Friedlander, Bacillus 
pyocyaneuS; etc., cause similar phenomena in ani- 
mals suffering from glanders. Wladimiroff asserts, 
however, that the reactions caused by these sub- 
stances differ from that of mallein. 

For diagnosis a dose must be used which causes 
no reaction in a normal animal, and this varies 
with different preparations. The typical reaction 
has two essential components : 1, A rise in tem- 
perature which begins in from six to twelve hours 
after the injection, reaches its maximum (from 40° 
to 42° C.) in from six to eight hours later, where 
it remains for a few hours, then gradually sinks, 
only to recur on the second day ; 2, an edematous 
and inflammatory tumor at the point of injection, 
which begins in from six to eight hours, and runs 
its course in from three to eight days, ending in 
resorption (Wladimiroff). Veterinarians gener- 
ally agree that mallein is a valuable diagnostic 
agent. Mallein also has been used in the treatment 
of glanders, but with rather doubtful results. 

Bacteriologic diagnosis is accomplished by culti- 
vating the bacilli from the abscess or secretions and 



458 INFECTION AND IMMUNITY. 

testing the virulence of the culture by animal ex- 
periments (guinea-pig). 
Agglutination. Normal horse serum agglutinates the glanders 
bacillus in dilutions of from 1/200 to 1/700, that 
of the diseased animal in a strength of from 
1/1600 to 1/2000. In some instances, however, 
infection causes no increase in the agglutinating 
power of the serum. Agglutinins are said to be 
formed more readily in man than in animals. 

IV. RHINOSCLEROMA. 

(See page. 402.) 

V. ACTINOMYCOSIS. 

Actinomycosis is a chronic infectious disease of 
man and animals, the lesions of which present, 
characteristically, a central mass of purulent and 
necrotic material containing colonies of "ray 
fungi/' about or through which is disposed an 
abundant growth of granulation or fibrous tissue. 
In young or rapidly progressing lesions the amount 
of purulent material is large, while in older lesions 
well formed connective tissue is more conspicuous. 
The disease prevails especially among cattle, al- 
though it is met occasionally in the horse, hog, 
sheep, dog, cat and other animals ; man is infected 
not infrequently. 

Although fungous threads had been found in 
diseases resembling actinomycosis in 1845 and 
later, Bollinger, in 1877, gave the first accurate de- 
scription of the disease in cattle, and in 1878 J. 
Israel described it as a new disease in man. A 
short time later Ponfick demonstrated the identity 
of bovine and human actinomycosis. 

The specific organism, Actinomyces bovis ct 



ACTINOMYCOSIS. 



459 






liominis, on culture media consists of a mass of del- The Fungus. 
icate threads which exhibit "true branching' 5 and 
which;, to a certain extent, segment to form 
"spores." The radially arranged groups of cells 
which occur as macroscopic granules in the pus of 
the actinomycotic abscesses, and which give to the 
organism the name of the "ray fungus/' are essen- 
tially a manifestation of parasitic existence, 
although colonies developing on media which 
contain serum or ascitic fluid may show a 
degree of "club" formation (Wright). Each 
granule represents a colony of organisms the 
members of which possess club-shaped extremi- 
ties, and in the center of the mass and 
extending from it are many of the delicate threads 
found in cultures of the organism. It grows on 
various culture media, often as a mold, and stains 
by Gram's method. 

The actinomyces is an organism of considerable Resistance. 
resistance. Cultures remain alive for one year or 
more when in a dried condition and the spores in 
one instance germinated after having been pre- 
served for six years. A temperature of 80° C. 
for fifteen minutes kills the spores (Berard and 
Nicolas). When suspended in bouillon, spores are 
killed in fifteen hours by direct sunlight, but when 
thoroughly dried, approximately ten days' expos- 
ure produced no injury. 

Attempts to place the actinomyces in a botanic 
system have resulted in many differences of opin- 
ion. By some investigators they are considered as 
an independent family midway between the hy- 
pliomycetes and the schizomycetes (bacteria), oth- 
ers place them under the hyphomycetes in the group 



460 



INFECTION AND IMMUNITY. 



Artificial 
Infection. 



Transmission 

and Infection 

Atria. 



of the streptothrix, while still others consider them 
as pleomorphous bacteria, placing them in the 
group cladothrix. Petruschky recognizes acti- 
nomyces, streptothrix, cladothrix and leptothrix as 
genera in the family trichomyces, the latter belong- 
ing to the order hyphomyces. Biological variations 
which have been encountered have led to the rec- 
ognition of several species of actinomyces, among 
which are a number of non-pathogenic forms. 
Wright limits the term actinomyces to those strains 
which produce colonies of club-shaped organisms 
in animal tissues. 

Many attempts have been made to transmit 
actinomycosis to animals by inoculating them with 
the diseased tissues of animals and man, and with 
pure cultures obtained from these tissues. Al- 
though a number of experimenters have reported 
positive results, the attempts usually have been 
fruitless. Probably Wright has been more success- 
ful than others in producing actinomycotic lesions 
in rabbits and guinea-pigs by the inoculation of 
pure cultures. Colonies of club-shaped organisms 
developed with considerable uniformity. In many 
instances the infection remains localized, not caus- 
ing the progressive and destructive changes which 
actinomycosis produces when it occurs naturally. 

The organism has been found on grains, straws 
and other kinds of feed, with which it may be im- 
planted in the soft parts of the mouth (gums, 
tongue), or in carious teeth. Transmission to man 
by eating the meat of actinomycotic cattle has not 
been noted. In man the disease is primary in the 
internal organs (lungs, intestines, liver, brain, 
etc.) in a large percentage of the cases, whereas 
"lumpy jaw" is rare. The disease extends locally 



ACTINOMYCOSIS. 



461 



by the gradual involvement of adjacent tissues, 
which in time become occupied by sinuses, ab- 
scesses and masses of connective tissue. Numerous 
"spores" and bacillus-like cells, having their source 
in the fungous threads, abound in the vicinity of a 
colony. The occurrence of such forms in leuco- 
cytes and other large mononuclear cells has led 
some to the view that the micro-organisms may 
be carried to neighboring tissues or to distant 
parts as cell inclusions. In cattle the disease usu- 
ally is more chronic than in man, more fibrous tis- 
sue is formed and metastases in internal organs 
are less frequent. In man the lesions are more 
purulent in character, large abscesses sometimes 
form as in the liver, and metastases in visceral or- 
gans are more common. Cases of general acti- 
nomycosis are occasionally met with in both cattle 
and man. 

Little can be said in the way of prophylaxis Prophylaxis 
against actinomycosis. Knowing the part that in- 
fected grains, straws, etc., play in instituting in- 
fection, the practice of biting or chewing grains or 
of using straws as toothpicks, evidently is one 
which affords opportunity for infection. The pres- 
ence of carious teeth has often been suggested as 
a predisposing condition for infection. 

Practically nothing is known concerning the de- 
gree to which susceptibility to actinomycosis pre- 
vails, and the question of immunity to the disease 
remains unexplored. The inability to reproduce 
the infection in animals at will renders a satisfac- 
tory study of these questions very difficult. The 
presence of large numbers of polymorphonuclear 
leucocytes in the vicinity of the organisms sug- 
gests, but does not prove, that they may have some 



Immunity and 
Susceptibility. 



462 INFECTION AND IMMUNITY. 

influence in combating the infection. Surely the 
abundant mass of connective tissue which develops 
about the abscesses and sinuses aids in confining 
the process to a definite region. 

That the iodid of potassium has a curative influ- 
ence on some cases of actinomycosis seems to have 
been well demonstrated. The principles by which 
it produces its effects are unknown. 

VI. MADURA FOOT. 

Mycetoma. Mycetoma, or Madura foot, resembles actinomy- 
cosis in the formation of abscesses, sinuses and 
granulation tissue, but it shows a peculiar predilec- 
tion for the foot, which probably is explained by 
the greater exposure of this part to infection. This 
disease differs from actinomycosis in that the 
course is more chronic and it is never accompanied 
by generalized infection. The bones are not in- 
volved so frequently as in actinomycosis. Granules 
similar to those of actinomycosis are found in the 
cells, which, however, do not assume the pro- 
nounced club shape seen in colonies of the ray fun- 
gus. 

Two varieties of the disease are known, one in 
which the granules are brown or black, and an- 
other in which they are white or yellowish; the 
latter is encountered much more frequently than 
the former. 

Pure cultures of the organism, which is called 
Streptothrix madurce (Vincent), were first ob- 
tained by Vincent in 1894, and have been studied 
by a number of observers since that time. It bears 
a close resemblance to the actinomyces and by some 
is considered a variety of this organism. Differ- 
ences between the black and white varieties are not 



OIDIOMYCOSIS. 463 

clearly set forth. The disease occurs in southern 
Asiatic countries, in northern Africa, and in the 
United States (rare). 

VII. INFECTIONS BY STREPTOTHRIX, CLADOTHRIX 
AXD LEPTOTHRIX* 

Cultures of streptothrix, differing from the streptothrix 
actinomyces, have been obtained from the lungs 
in a number of instances and in various pountries. 
They have been found in such lesions as broncho- 
pneumonia, or more extensive consolidation of the 
lungs, and in cases of empyema. In other instances 
organisms which have been classed, some as strep- 
tothrix, others as cladothrix, have been cultivated 
from processes which resembled actinomycosis. 

Nocard considers a streptothrix as the cause of 
farcin du bceuf (farcy of cattle), a disease encoun- 
tered especially in the countries of southern Eu- 
rope, and similar organisms have been cultivated 
from suppurating or granulomatous foci in other 
animals. 

Leptothrix buccalis, a thread-like organism 
which does not form branches and, hence, is not an 
actinomyces nor a streptothrix, is frequently found 
as a saprophytic organism in the mouth cavity, and 
a similar fungus, Leptothrix vaginalis, has been 
encountered in the vagina. Although organisms 
of this type are relatively harmless, they have occa- 
sionally been found in diseased conditions of the 
tonsils and pharynx. 

VIII. OIDIOMYCOSIS. 

In 1894 Gilchrist described a skin disease, which 
has since been known as blastomycetic dermatitis, 
or blastomycosis or oidiomycosis of the skin. From 
a second case he cultivated a fungus which at first 



464 INFECTION AND IMMUNITY. 

"Biastomy- he was inclined to consider as an oidium, but later 

cetic" Der- . 

matitis. called a blastomyces. Since that time many simi- 
lar cases, especially in Chicago and the adjacent 
territory, have been discovered and reported by 
Wells, Hektoen, Hessler, Hyde and Montgomery, 
Eicketts and others. In many instances the spe- 
cific fungi have been cultivated. 
Systemic Further investigations by Eixford and Gilchrist, 

Oidiomycosis. , ... ° ^ J __ 

. J3usse, Ophuls and Momt, Hyde and Montgomery 
and others have brought to light the existence of 
systemic intections by fungi which resemble 
closely those found in blastomycetic dermatitis, 
and, in fact, cases in which the" infection primar- 
ily was limited to the skin have gone on to general- 
ized infection. The Saccliaromycosis hominis of 
Busse and Curtis, blastomycetic dermatitis, gen- 
eralized blastomycosis, and about a dozen cases in 
California, which at one time were considered to 
be of protozoon etiology (Eixford and Gilchrist), 
are closely related or identical processes which have 
as their cause a group of fungi, the individual 
strains of which may show considerable differences. 
Nature of In those cases usually described as blastomycetic 
dermatitis or systematic blastomycosis, the fungus 
proliferates in the tissues by budding, and 
is found chiefly in the intraepithelial and 
subcutaneous abscesses, and in the granula- 
tion tissue and nodules of internal organs. 
Its appearance in culture media and its bio- 
logic properties are subject to considerable 
variations, at one time growing as a mold, at an- 
other time more like the typical oidium, and again 
resembling some form of yeast. Eicketts considers 
that the genus oidium is sufficiently broad to in- 
clude all the types which have been described, and 



Fungi. 









OIDIOMYCOSIS. 465 

that blastomyces is too narrow. The organisms 
which have been cultivated from the cases in Cali- 
fornia grow as molds, and they differ from those 
described by Gilchrist, Hektoen, Eicketts and oth- 
ers in that they form endospores and apparently do 
not bud in the tissues of the host (Ophiils, Wol- 
bach). Ophiils calls this parasite Oidium cocci- 
dioides, agreeing with Eicketts as to the generic 
character of the group. 

The skin infection usually appears as a coarse Histology. 
warty and ulcerative lesion, in ■ which the large 
papillae and cutaneous areola are beset with mi- 
nute abscesses; the process extends gradually and 
eventually may involve large areas. Histologically, 
• the tissue shows an enormous epithelial hyper- 
plasia with intraepithelial abscesses, and a richly 
cellular, granulomatous condition of the subepithe- 
lial tissue, in which giant cells and small abscesses 
are found. When the disease is systemic, various 
internal organs, especially the lungs, spleen and 
kidneys, are the seats of abscesses and nodules 
which contain the parasites in immense numbers. 
The lungs show lobular or more extensive consoli- 
dation. 

The skin infection occasionally follows slight infection 
traumatism, while in other instances no predispos- 
ing condition is known by the patient. The occur- 
rence of cutaneous lesions in crops has been noted, 
and suggests that in some instances they may orig- 
inate as embolic foci from a pulmonary lesion 
which later heals or becomes latent. In the sys- 
temic infection the primary lesion appears to be 
in the lungs in most cases, from which the blood 
and other organs, including the skin, may be in- 
vaded. Pulmonary oidiomycosis simulates pul- 



Atria. 



466 INFECTION AXD IMMUNITY. 

monary tuberculosis. In extensive involvement of 
the lungs the organisms may be demonstrated in 
the sputum. At present nothing is known concern- 
ing immunity to these infections. 

Thrush. 

Ophiils very properly suggests that thrush 
should be considered as one form of oidiomycosis. 
Thrush is of particular interest because of the early 
date at which its parasitic nature was recognized. 
Langenbeck and Berg, in 1839 and 1841, are cited 
as the discoverers of the fungus, and they repro- 
duced the disease by inoculations with fragments 
of the membrane. The parasite was studied a little 
later by Grub}^, Eobin and others, and the latter 
gave it the name of Oidium albicans. G-rawitz ob- 
tained it in pure culture in 1877 and demonstrated 
its pathogenicity for dogs and rabbits. 

Cultures of the organism show differences in 
size, morphology, chemical activities and methods 
of proliferation, although the variations are hardly 
so wide as those found among the fungi cultivated 
from cases of blastomycosis." 
systemic Although thrush usually is considered a rather 
infection, harmless affection, Virchow long ago showed that 
its filaments may penetrate the submucous tissues 
and even the lumens of blood vessels. In rare in- 
stances systemic infection, with abscesses in the 
brain, kidney and spleen or with nodules in the 
lungs, has been noted; in these cases the condi- 
tions resemble those found in systemic "blastomy- 
cosis." 

The healthy person has little or no susceptibility 
to thrush, although a few cases of infection have 
been noted in individuals who were otherwise nor- 



OIDIOMYCOSIS. 467 

mal. Customarily it attacks only those who are 
in a low state of vitality, as poorly nourished chil- 
dren or those in advanced age, or those whose re- 
sistance is much lowered by some other disease (ty- 
phoid, diabetes, etc.). 

Phagocytosis of yeast and oidium-like cells takes Phagocytosis 
place when they are placed in the abdominal cav- 
ity of experiment animals (guinea-pigs). A num- 
ber of leucocytes may fuse to form a plasmodial 
mass around one or more of the parasitic cells. 
Eoger and Xoisette caused an increase in the re- 
sistance of rabbits to thrush infection by the intra- 
venous injection of small doses of the parasite. Ac- 
cording to Xoisette, an immune serum agglutinates 
only the strain used in the immunization. 

Infections of other animals (horses, cattle) by 
oidium-like organisms, the trichophyton and other 
fungi which cause superficial diseases in the skin 
of man, and other fungi (aspergillus, mucor), 
which occasionally are pathogenic for man, will not 
be discussed. 



GROUP V. 



PROTOZOON INFECTIONS. 
I. MALARIA. 

Etiology. The etiology of malaria, which for long was 
supposed to be associated with impure and swampy 
atmospheres (malaria is from maP aria, Italian 
meaning bad air), remained unknown until 1880, 
when Laveran discovered ameboid, half-moon 
shaped and flagellated forms of a parasite in the 
blood of the patients. In following years Golgi, 
Grassi, Marchiafava and Celli and many others 
took prominent parts in working out the different 
forms of parasites, their sexual characters and their 
relation to the different types of malaria. 

Ross and The conception that mosquitoes may be influen- 
tial in transmitting malaria is a very old one and 
its origin is unknown. In 1894 Manson suggested 
that the malarial organism may utilize the mos- 
quito as an intermediate host where, after under- 
going further development, it again becomes in- 
fectious for man. He was inclined to think that 
the flagella are reproductive forms, which are 
essential for an extra corpus life of the parasite. 
The proof of this came from MacCallum in 1897, 
who showed that the flagellated forms are really 
spermatozoites, the function of which is to im- 
pregnate female cells of the parasite. This was 
observed first in relation to halteridium, one of 
the organisms of avian malaria, and later in rela- 
tion to the parasites of human malaria. 

In the same year Ross found the pigmented, 
half-moon shaped parasites of asstivo-autumnal 



MALARIA. 



469 



Species of 
Plasmodium. 



Fever. 



fever in the stomach of the anopheles mosquito. 
Through the work of Ross and others it is now 
established that the malarial parasite undergoes 
further development, a sexual cycle, in anopheles, 
and that man is inoculated only by the bites of 
such infected insects. From the standpoint of 
the zoologist, man is an intermediate host for the 
parasite, since the latter undergoes its higher de- 
velopment only after it reaches the mosquito. 

The malarial parasites of man belong to the 
class of Sporozoa; order, Coccidiomorpha ; family, 
Hemosporidia ; genus, Plasmodium. The follow- 
ing are the names given to the three species: 1. 
Plasmodium prsecox (parasite of sestivo-autumnal 
fever) ; 2. Plasmodium vivax (of tertian fever) ; 
3. Plasmodium malariae (of quartan fever) . 

When the blood of one suffering from tertian i 
fever is examined at the end of the febrile parox- 
3 r sm, or at the beginning of the afebrile stage, the 
parasites are found within the erythrocytes as pale, 
rather clear bodies, about one-fifth the diameter of 
the corpuscle, and in fresh specimens showing an 
active ameboid movement. They are very difficult 
to recognize in unstained specimens. They increase 
in size gradually, and after eighteen hours, when 
they begin to acquire pigment, they are recognized 
more easily. After twenty-four hours the pig- 
ment has increased markedly and the erythrocytes 
are swollen and pale. In stained preparations the 
periphery of the parasite stains more deeply than 
the center and gives it a pronounced ring form. 
At the end of thirty-six hours they have increased 
noticeably in size and their ameboid motion is 
less. Shortly before the next attack — i. e., forty- 
six to forty-eight hours after the preceding one — 



470 



INFECTION AND IMMUNITY. 



Sexual 
Cells. 



Segmentation the pigment assembles into one or two groups in 
s ce"is. the center of the parasite and clear hyaline points 
begin to appear. These are the young endocellular 
parasites which are formed by division of the nu- 
cleus of the mother cell. They gradually increase 
in size and number, and as the red corpuscles disin- 
tegrate they are discharged, from fifteen to twenty- 
five in number, as young parasites. This completes 
the cycle, an asexual cycle, which has lasted forty- 
eight hours, and the young forms then begin a 
. new cycle after penetrating other red corpuscles. 
The mother cell is called the sporocyte and its 
offspring are merozoites, and the process of divi- 
sion schizogony. 

In addition to the asexual cell just described, 
two sexual cells, a male and a female, grow to 
adult size in the erythrocytes, acquire pigment and 
eventually become free. They differ from the 
asexual cell in that the pigment continues to be 
uniformly distributed, and neither gives rise to 
young parasites by division. The male cell (micro- 
gametocyte, 8-9 microns) has a clear protoplasm 
and is smaller than the female (macrogamete, 
10-14 microns) ; the female has a granular proto- 
plasm. There are many more male than female 
cells. They undergo no further development in 
the body of man, and in order that the sexual pro- 
cess be completed the two cells must first gain en- 
trance into the stomach of the female anopheles 
mosquito. 

A further step in the sexual process may be seen 
in drop preparations of the blood, although this 
step does not occur in the human body. Ten to 
twenty minutes after such a preparation has been 
made the male cells, after a period of agitation, 



Impregnation 



MALARIA. 



471 



Formation of 
Sporozoites. 



discharge from four to eight long, thin flagella 
(microgametes or spermatozoa), which thrash 
about violently and eventually come in contact with 
a female cell, which they enter and become un- 
recognizable. 

This same process is instituted and completed Life in the 
(sporogony) in the stomach of the mosquito, the 
penetration of the female cell by the spermatozoon 
resulting in the impregnation of the former. Fol- 
lowing impregnation, the female cell gradually 
assumes a worm-like or sickle shape (ookinet), 
penetrates the wall of the stomach and becomes 
encapsulated (oocyst). Forty-eight hours after 
the mosquito has sucked malarial blood all the 
female cells have reached this stage and no more 
free parasites are found in the stomach. 

About five days after the blood was taken the 
oocyst has increased in size about six times and 
has formed within itself a number of small 
spheres, which are called daughter cysts or sporo- 
blasts. The latter soon acquire a finely striated ap- 
pearance, which is due to the formation of hun- 
dreds of "germinal rods" or sickle-like bodies 
(sporozoites). The latter are nothing less than 
young malarial parasites, which are thrown into 
the body cavity by the rupture of the oocyst, and 
are carried to the salivary glands of the mosquito 
by the lymphatic circulation. If the mosquito has 
been kept at a temperature of 24° to 30° C. these 
sickle forms first appear in the salivary gland after 
eight to ten days. Such are the cells which are 
inoculated into man by the bite of the mosquito. 
The changes which they undergo before they ap- 
pear as clear oval bodies in the erythrocytes are 
unknown. 



472 INFECTION AND IMMUNITY. 

Parasite of The asexual cycle of the quartan parasite is 
U Fever! identical with that of the tertian, with the excep- 
tion that seventy-two hours are required for its 
completion. It contains more pigment, and when 
division takes place eight, or at most fourteen, 
young parasites are formed, in contrast to the 
fifteen to twenty-five of the tertian parasites. The 
erythrocytes do not become large and pale (Euge). 
The sexual cells practically are indistinguishable 
from those of the tertian parasite, although they 
are, on the whole, slightly smaller. The sexual 
cycle also is completed only in the body of the 
female anopheles mosquito, and is identical with 
that of the tertian parasite. 

Parasite of The parasite of sestivo-autumnal fever is one- 

Aestivo-Au- 

tumnai Fever, half to two-thirds the size of the tertian parasite, 
a difference which is constant in the various stages 
of development of the asexual cell. It divides 
eventually into eight to twenty-five young para- 
sites, the cycle occupying from twenty-four to 
forty-eight hours. 
'Half-moon" Here, as in quartan fever, the erythrocytes do 
not become swollen and pale, but even appear 
darker in color, because of some shrinking (Euge). 
The sexual cells in aestivo-autumnal fever are 
characteristic. Whereas they at first do not differ 
in shape from the asexual cells, as they grow older 
they gradually assume the shape of a half moon in 
one edge of the erythrocyte, reaching a length 
equal to one and one-half diameters of the red cell. 
At this time a fine line drawn across the concavity 
of the parasite represents the margin of the ery- 
throcyte. This form is only temporary, however; 
they subsequently assume first a spindle and then 
a spherical form. As in the other parasites, the 



Cells. 



MALARIA. 473 

male cell is rather clear and the female granular. 
When mounted in a hanging drop the male cell 
liberates nagella, which penetrate the female cell. 
This does not occur in the human body. In this 
respect, and also in the completion of the sexual 
cycle in the body of the mosquito, they resemble the 
other two parasites. 

The parasites of tertian and quartan fevers un- 
dergo division while they are in the circulating 
blood, and when peripheral blood is examined at the 
end of the afebrile stage the young cells may be 
found extracellular. This is not the case, how- 
ever, in the sestivo-autumnal fever. In this in- 
stance, for unknown reasons, the adult cells with- 
draw to the internal organs, especially the spleen, 
bone-marrow and brain, where division takes place 
in the minute vessels. Hence if the peripheral 
blood is examined preceding and during the febrile 
stage few or no dividing cells or young parasites 
are seen. 

Following inoculation by an infected mosquito, incubation 
ten to twelve days are required for the onset of a 
paroxysm. In rare instances the incubation period 
may be as short as five to six days. This probably 
depends to some extent on the number of organisms 
inoculated. Malarial infection of the mosquito 
is not transmitted to the offspring the latter,* 
hence the bites of young mosquitos do not convey 
the disease unless they also have sucked malarial 
blood. The conditions are different in relation 
to Texas fever, in which the infection is trans- 
mitted by the female tick to her young. 

The aestivo-autumnal parasite apparently is virulence. 
more virulent than the tertian or quartan. Not 

* This is questioned by Schaudinn. 



the Parasites. 



474 INFECTION AND IMMUNITY. 

all cases of tertian or quartan fever are equally 
severe, and these variations may depend on differ- 
ences both in virulence and in the resistance of in- 
dividuals. When all the parasites divide within a 
period of two to four hours, the paroxysm is more 
intense but shorter than when division extends 
over six to eight hours '(Kuge in relation to ter- 
tian fever). Some of the severer symptoms are 
due to the localization of the parasites (brain and 
intestines), rather than to special toxicity. 
Relation of The melanemia of malarial fevers is due to the 
the'Sfoiogy of fact that the parasites absorb the hemoglobin from 
the erythrocytes, transform it into melanin by 
their metabolic activities and liberate the melanin 
at the time of cell division. The anemia results 
from destruction of the erythrocytes. 

The cause of the fever and its periodic recur- 
rence is more difficult to explain. As stated above, 
the fever begins in both tertian and quartan fevers 
at the time division forms of the parasites are en- 
countered in the peripheral blood. Although all 
the parasites do not divide simultaneously, the 
process is complete within a period of four to 
eight hours and the paroxysm begins early in this 
Fever and period. It is quite natural, then, to infer that by 
the division of the parasite and the escape of the 
young cells from the erythrocytes, toxic substances 
are thrown into the circulation, and that the febrile 
reaction is due to the action of these toxins. 
Methylene blue has the power of preventing seg- 
mentation of the parasites (Ehrlich), and it has 
been shown that the paroxysm of fever may be 
averted by administering methylene blue at the. 
proper time. This corroborates the view that the 
segmentation of the parasites causes fever in some 



Schizogony. 



MALARIA. 



475 



way. The paroxysm would seem to represent the 
time required for the exhaustion of the toxins set 
free at the time of the cell division.* 

On the basis of the conditions just cited, the 
brief duration, sharp limitation and regular re- Duration of 
currence of the paroxysms in tertian and quartan 
fevers become intelligible. In a similar manner 
the longer paroxysms and shorter intermissions 
which characterize the typical aestivo-autumnal in- 
fection (i. e., in first attacks) are related to the 
habits of division of the corresponding parasite. 
All the cells do not divide within a relatively short 
period, as in tertian and quartan fevers, but the 
process of division rather stretches out over from 
twenty-four to forty-eight hours. This accounts 
for the longer duration of the paroxysm. When 
the last cells of one generation are dividing, per- 
haps after the fever has gone down, the first cells 
of the succeeding generation are well on toward 
maturity and their division within a short time 
inaugurates a new paroxysm; the brief intermis- 
sion would seem to be explained by this condition. 
As the disease lasts longer, or as relapses develop, 
the periods of division of the parasite are less 
sharply limited and a course with an irregularly 
continuous ( ?) fever may be established. 

Quotidian malarial fever is caused either by 
a double infection with tertian parasites or a 
triple infection with quartan parasites. In either 
instance a generation of parasites matures and 
divides every twenty-four hours. The cause of 



Quotidian 
Fever. 



* Kosenau, Parker, Francis and Beyer produced a typical 
paroxysm in a healthy person hy injecting filtered serum 
taken from a tertian patient during the chill. This was 
intoxication, not infection. 




476 INFECTION AND IMMUNITY. 

the double or triple infection is not known definite- 
ly. In some instances it is possible that successive 
inoculations by different mosquitoes has occurred. 
On the other hand a fever which is primarily ter- 
tian or quartan may gradually change into the 
quotidian variety, and in this condition it is pos- 
sible that the organisms may gradually separate 
themselves into two or three distinct generations, 
which reach maturity on successive days. 
Mixed l n other instances mixed infection with two 

Infections. . . . . 

kinds oi parasites is encountered. This is usually 
aestivo-autumnal fever combined either with ter- 
tian or with quartan. Either the aestivo-autumnal 
may be primary on the one hand or the tertian or 
quartan on the other. The clinical course is com- 
plicated correspondingly. It is doubtful if tertian 
infection is ever mixed with quartan. Ruge speaks 
of experiments by Dr. Mattei which indicate that 
a mixed infection does not .continue indefinitely 
as such. A patient suffering from quartan fever 
was inoculated with aestivo-autumnal blood; in 
time all the quartan parasites disappeared, leav- 
ing only the aestivo-autumnal. 

In malarial cachexia there is not only an in- 
'sufficiency of the blood-forming organs, but other 
parenchymatous organs have suffered as a result 
of prolonged intoxication. The blood-forming or- 
gans can not keep pace with the destruction of the 
erythrocytes. 

Trigeminal and supraorbital neuralgias and 
periodic headaches occur sometimes as accompani- 
ments of malarial infection, even when there is 
little or no fever, and no parasites may be dis- 
coverable in the blood. That they are malarial in 
origin is concluded from the fact that they subside 
under quinin treatment. 



MALARIA. 



477 



"Black-water 
Fever." 



In some forms, and particularly in sestivo- Cerebral 
autumnal fever, cerebral symptoms (e. g., coma) nai Symptoms. 
are marked by accumulations of the parasites in 
the small vessels of the brain; the vessels may be 
completely occluded. The conditions are similar 
in the small vessels of the intestines in malarial 
diarrheas. 

The so-called "black-water fever," or hemo- 
globinuric fever, is not a special form of malaria, 
but a complication which, it is thought, is pre- 
cipitated by insufficient or improper administra- 
tion of quinin (Koch and others). It is most fre- 
quent in the tropics, hence in aestivo-autumnal 
fever, but may occur in the tertian and quartan 
types. Various observers have found that in all 
the way from 56 per cent, to 97 per cent, of the 
cases quinin precipitated attacks. Stephens and 
Christopher were not able to exclude quinin as a 
factor in any of the cases they encountered. The 
essential process is a massive destruction of the 
erythrocytes which is entirely out of proportion to 
the number of cells occupied by parasites: few or 
no parasites may be present. The amount of 
hemoglobin thus liberated is so great that it is ex- 
creted largely by the kidneys; anuria may result 
from occlusion of the tubules by pigment. How 
the quinin, or the quinin plus parasites, produce 
this extensive hemolysis is entirely obscure; the 
effect is that of an intense intoxication, in which 
the erythrocytes suffer primarily and chiefly. 

The essential epidemiologic features of malaria Epidemiology. 
are the following : It prevails especially in tropical 
and subtropical zones and less in temperate zones. 
It is most abundant in low, swampy regions, and 
in other places which afford quiet streams, ponds 



478 



INFECTION AND IMMUNITY. 



or other standing water. Malaria is not directly 
contagions. In order to become infected it is 
necessary, customarily, for one to enter or be in 
close proximity to a "malarial district." That 
the virus is not carried far from an infected dis- 
trict is shown by the exemption of the crews of 
vessels which lie within two or three miles of such 
a district. Infection has long been supposed to 
take place chiefly by night. The disease may be 
introduced into new regions (of suitable climate) 
by the importation of malarial subjects. These 
and many other phenomena of malaria which were 
once very obscure have been cleared up by the 
mosquito theory. 
Anopheles. There are many species of anopheles and they 
are distributed throughout the world in warm and 
moderate climates. Anopheles maculipennis is 
the most numerous species, and for it, as well as 
for Anopheles punctipennis, Howard has found 
several natural breeding places in this country. 
It is probable that many, but not all, species of 
anopheles may transmit malaria. The female 
only is a blood-sucker, the male living on vegetable 
material exclusively. After the female has ob- 
tained blood from man or another mammal it flies 
to a suitable pond or other collection of water, 
where it deposits its eggs. 
Development "The adult mosquito lays its eggs on the surface 
of the water. The eggs float on the water for 
some days (two to four), after which they hatch 
and permit the escape of the larva. 

"The larva is a free-swimming, worm-like ani- 
mal, which eats greedily and grows rapidly, cast- 
ing its skin several times in the process, till it 
reaches its full development. At this stage it sud- 



MALARIA. 479 

denly changes its form; casting its skin, the worm- 
like larva assumes a comma shape and so becomes 
th'e pupa or nympha. 

"During the pupal period the insect ceases to 
eat; profound anatomical changes take place with- 
in the pupal skin, whereby the masticatory mouth- 
parts of the larva are converted into the suctorial 
apparatus of the adult insect or imago. After a 
certain number of days the pupa case ruptures and 
the adult insect is liberated, furnished with wings 
and legs adapted for a life in the air." (James 
and Liston.) 

In one instance Howard found the life cycle of 
Anopheles maculipennis to be: "Egg stage, three 
days; larval stage, sixteen days; pupal stage, five 
days, making a total period in the early stages of 
twenty-four days." The rapidity with which this 
process takes place depends largely on the tem- 
perature; it is more rapid in the hot weather of 
July and August than in the cold days of May. 
Anopheles usually does not lay its eggs in tin cans 
or barrels of water, but preferably in more open 
or cleaner water. Excavations which have become 
filled with water are favorable places, as are also 
collections of water from springs. 

The anopheles leads an adult life for many JXhllSi? 1 
months and may even hibernate under suitable 
conditions either in the adult or larval form. It 
is generally stated that the insects do not fly more 
than half a mile from their breeding and feeding 
grounds. Their dispersal certainly extends beyond 
these limits, however. James and Liston enumer- 
ate the following methods of dispersal : 1. By 
direct flight over considerable distances. 2. By 
the eggs and larvae being carried in streams and 



480 



INFECTION AND IMMUNITY. 



Prophylaxis. 



General 
Measures. 



canals. 3. By a multiplication of successive short 
nights by adults. 4. In conveyances. 

Anopheles avoids high winds and rains, seeks 
shelter on excessively hot days and feeds and bites 
chiefly or only after sunset and before sunrise. 
The latter habit confirms the old belief that ma- 
larial infection occurs chiefly at night. 

For further details as to the morphology and 
habits of the insect in its different stages, and for 
differentiation of the different genera and spe- 
cies, one should consult a textbook of entomology, 
or, for example, the book on "Mosquitos," by How- 
ard (McClure, Phillips & Co., New York).- 

Individual proplrylaxis may be accomplished and 
maintained by taking small daily doses of quinin, 
or larger doses (1 gram) every few days. One who 
has had malaria may likewise prevent recurrence 
by suitable quinin treatment. Quinin has the 
power of preventing division of the parasites, and, 
therefore, the power of . preventing the paroxysms. 
"K. Koch's procedure consists in this, that one 
takes a gram of quinin every tenth and eleventh 
day, and if fever still develops, every ninth and 
tenth day." (Euge.) 

Other points in individual prophylaxis are, first, 
the application of ethereal oils (clove oil, oil of 
pennyroyal) to the exposed skin, and, second, the 
use of mosquito netting. 

The important practices for general proplrylaxis 
are the following: 1. The draining of swampy 
places and of pools of water where anopheles may 
deposit its eggs. This in many instances manifest- 
ly can not be accomplished. 2. Covering pools of 
water with petroleum. This is to a degree success- 
ful. Every square meter requires */2 liter of pe- 






MALARIA. 481 

troleum (Kerschbaumer), and the oil must be 
added fresh every seven or eight days. The layer 
of oil excludes the air from the larval mosquitoes 
and they drown. If fresh oil is not added occa- 
sionally new eggs may hatch. 3. Koch's method of 
extermination of malaria. This consists of the 
searching out of all cases of malaria and the de- 
struction of the parasites by appropriate quinin 
treatment. Koch practiced this method in an in- 
fected locality of New Guinea and in a relatively 
short time freed it of malaria. If all the plasmodia 
in a community are destroyed the disease can not 
again become endemic unless it is introduced from 
without or unless infected mosquitoes are imported. 
Manifestly this method must be practiced on an ex- 
tensive scale in order to render it permanently 
successful. It seems to have been demonstrated, 
however, that the number of cases in any given 
locality may be materially decreased by pursu- 
ing it. 

So far as is known, susceptibility to malaria is immunity. 
universal. The belief is very general that one 
attack of malaria not only does not protect against 
reinfection, but even predisposes to it. Two facts, 
however, show that acquired immunity (relative 
or absolute) is possible. First, in certain regions 
of Africa where malaria is endemic the adult na- 
tives rarely suffer from the disease, and then only 
from light attacks, whereas European visitors con- 
tract the disease in severe form. The cause of this 
immunity was explained by Koch. "Koch found 
that the native adults of malarial countries were 
free from malaria, but that the children suffered 
almost universally from malarial diseases. If 
they recovered from the original infection they 



482 INFECTION AND IMMUNITY. 

became immunized in time through continued new 
attacks or relapses, the number of malarial chil- 
dren gradually decreased with their age, and in the 
vicinity of the tenth year the only evidence, in 
general, of a previous infection was an enlarged 
spleen, and even this disappeared during puberty, 
so that the adult natives finally appeared as 
healthy and malaria-immune persons." (Huge.) 
The objection raised by many that such immunity 
is not observed in Italy and other civilized coun- 
tries where malaria is endemic, is met by the fact 
that the disease in these countries is not permitted 
to run an uninterrupted course. Treatment with 
quinin is instituted and the immunizing process 
is thereby broken off. Koch also established that 
immunity against one type of parasite is not effi- 
cient against other types. 

Second, in civilized countries it has often been 
noted that subsequent attacks are of a milder char- 
acter than the primary; the disease may in time 
"wear itself out," even without quinin treatment. 
Huge gives as an accompaniment of this immuniz- 
ing process the occurrence of the sexual cells in 
large numbers, even up to 50 per cent, of the total 
number of parasites (tertian fever). In such 
cases large numbers of the parasites die before 
they reach maturity, their death being indicated 
by shrinking and clouding of the cells and altera- 
tions in or disappearance of the chromatin. It is 
somewhat characteristic of quartan fever, and still 
more so of sestivo-autumnal, that the sexual cells 
are much more numerous in recurrences than in 
primary attacks. One may be able to differentiate 
a relapse from the primary attack by the number 
of sexual cells encountered (Kuge). 



TRYPANOSOMIASIS. 



483 



Xothing in the way of serum therapy has been 
accomplished, and it is doubtful if any serum 
could equal quinin in efficacy. 

MALARIA OF BIRDS. 

What is considered as true malaria also occurs in birds. Proteosome. 

One of these diseases is caused by a proteosome (Pro- 
teosoma Labbe, Oystosporon danieleicsky, Hemameba re- 
licta ) . Sparrows, hawks, buzzards, crows and pigeons 
are affected. Like the malarial parasites in man, the 
parasite enters the erythrocytes and has both a sexual 
and an asexual cycle of development, the latter taking 
place in the infected animal, the former in the stomach 
of the common mosquito {Culex pipiens) . Hence in its 
development proteosoma is perfectly analogous to 
Plasmodium. The disease is transmissible from bird to 
bird by the inoculation of infected blood. 

Halteridium is still another hemosporidium which in- Halteridium. 
fects birds. It was in the study of this organism that 
MacCallum first saw the phenomenon of impregnation. 
All the cells seen in the blood appear to be divisible into 
male and female, and although MacCallum had seen im- 
pregnation in microscopic preparations the life cycle for 
a long time was obscure. Recently Schaudinn has found 
that the sexual cycle is completed in Culex pipiens. He 
considers the organism to be a trypanosome. "I have 
been able to prove that the halteridium is the sexual 
stage of a trypanosome which multiplies in the common 
mosquito — Culex pipiens — and after a complicated mi- 
gration through the body of the mosquito is again in- 
troduced by its bite into the blood of the owl, where, 
after a period of sexual multiplication, it is transformed 
into the well-known male and female halteridium." 



II. TRYPANOSOMIASIS. 

Gruby created the genus Trypanosoma in 1843, 
when he gave the name of Trypanosoma sanguinis 
to a flagellate protozoon which he found in the 
blood of frogs. Since that time similar organisms 
have been found in the bloods of many animals and 
the genus Trypanosoma has grown to considerable 



Genus 
Trypanosoma. 



484 IXFECTION AXD IMMUNITY. 

dimensions. It is not improbable, however, that 
a number which now bear independent names will 
be shown to be identical. This suggests itself par- 
ticularly in relation to trypanosomiasis in horses, 
in which the infections are known under four sep- 
arate names in different countries, and the para- 
sites are given separate specific names. The study 
of these infections is so young and has been prose- 
cuted in such widely separated countries that the 
existing chaos is quite natural and can be adjusted 
only as time and circumstances permit of close 
comparative study. Until such a time the prevail- 
ing views as to independence of species and of in- 
fections must be recognized. 
Morphology. Trypanosomas vary a great deal in size and mor- 
phology. Koughly, they are from one to five mi- 
crons thick and fifteen to forty-five microns long, 
including the flagellum. All species possess active 
eel-like movements, some traveling rapidly, others 
slowly. A long, actively-motile flagellum projects 
from the anterior end, and where it joins the cell 
body is continuous with an "undulating mem- 
brane," which extends along a border of the or- 
ganism to a point near the centrosome or micronu- 
cleus in the posterior portion of the cell. The 
centrosome is sometimes spoken of as analagous 
to the "eye spot" of some other protozoa. The un- 
dulating membrane is more or less wavy or folded 
and its breadth varies. The centrosome presum- 
ably has a close relationship to the undulating 
membrane, and, through the latter, with the flagel- 
lum. The nucleus is in the anterior portion of 
the parasite. In relation to some species a con- 
tractile vacuole is spoken of. An endoplasm and 
an ectoplasm may be differentiated. 



TRYPANOSOMIASIS. 



485 



Division of trypanosomes is nearly always longi- Division. 
tndinal, rarely transverse. According to Plimmer 
and Bradford., conjugation may occur, "followed 
by an ameboid stage and division by segmenta- 
tion." The ameboid stage at times occurred inde- 
pendently of conjugation. (Musgrave and Clegg.)* 
In the process of longitudinal fission the order of 
division of the different parts of the cell is as fol- 
lows : 1, Centrosome ; 2, flagelium ; 3, nucleus and 
protoplasm (Laveran and Mesnil). After division 
has occurred the two cells may remain" attached 
at their posterior ends for some time. By a re- 
peated division of young cells, the posterior ends 
remaining attached, rosettes are said to be formed. 
Others consider rosette formation as a phenomenon 
of agglutination. Possibly both phenomena occur. 

Trypanosomas are differentiated on the basis of Differentiation. 
size, pathogenicity, motility and certain points in 
morphology, as the position and size of the micro- 
nucleus or centrosome, the presence of a contractile 
vacuole, the size and tinctorial qualities of the 
nucleus, the degree of granulation of the proto- 
plasm and the location of the granules, appearance 
of the undulating membrane, length of flagelium 
and shape of the posterior non-flagellated end. 



TRYPANOSOMIASIS IX MAX. 

Xepreu in 1898 first found trypanosomes in 
the blood of man in Algiers in eight cases. His ob- 
servations were passed over temporarily. The para- 
site bears his name (T. neprevi). Again in 1901 
Forde discovered similar parasites in Western 



Trypanoso- 
ma tic Fever. 



* Knowledge is very deficient concerning the questions of 
conjugation and sexual cycles. An exception is to be made in 
relation to halteridium, a parasite of bird malaria, which is 
a trypanosome, according to Bchaudlnn. (Sec page 4.x::.) 



486 INFECTION AND IMMUNITY. 

Africa (Gambia), and since that time a number 
of cases of "Gambian fever" or trypanosomatie 
fever in man have been imported. In this in- 
stance the parasite was called T. gambiense by Dut- 
ton and T. hominis by Manson. The disease is 
said to follow the bite of a tsetse-fly (Glossina 
palpalis), at least in some instances. The tissues 
around the bite become inflamed and in from a 
few days to two weeks recurring attacks of fever 
set in, and a patchy and ringed erythematous erup- 
tion appears on the skin. Forde gives as the 
chief clinical findings in his case : „ 1, the irregular 
intermittent temperature; 2, the edematous con- 
dition of the face and lower extremities; 8, the 
rapid and variable pulse and respiration, unac- 
companied by any evident cause ; 4, loss of weight, 
with marked debility, wasting and lassitude; 5, 
the persistence of these symptoms and their re- 
sistance to treatment. The parasites, are most 
numerous in the blood at the time of the febrile 
attacks. Recovery has not been reported. 
Sleeping Sleeping sickness has been endemic in certain 
districts of Africa for a long time, and, although 
confined to a very limited district at one time, it ap- 
pears now to have extended to distant parts. Speak- 
ing of trypanosomatie fever and sleeping sickness 
collectively, E.uata says that while originally con- 
fined to a small district in Western Africa between 
the latitudes 15' North and 15' South, it is now 
found one thousand miles up the Congo (Bangola, 
Stanley Falls) and in East-central Africa on the 
shores of the Victoria Nyanza Lake. "Now it ex- 
tends from the mouth of the Katonga River 
through Uganda (1901, Cook), Kome Island. 
Busaga, Buvuma, Kavirondo, Kisumu, Lumbwa, 



TRYPANOSOMIASIS. 



487 



Homa, Kasagunga, Lusinga Island, the eastern 
shores of the lake, joining the south of the bound- 
ary river Gori in the Udemi district of the Sultina 
of Obo" (Euata). 

Its extension supposedly has been facilitated by Occurrence. 
rapid transit. "The disease is most prevalent 
amongst the inhabitants of low-lying shambas (ba- 
nana and potato plantations) in places along the 
shores of the Victoria Nyanza, or in wooded dis- 
tricts not far from the water" (Christy). Those 
living on high ground are much less infected than 
those living in the low moist places near water. A 
great deal of stress is laid on its close association 
with inland bodies of water. 

It apparently has no relation to sex, age, sea- 
sons, food or drinking water, and is related to oc- 
cupation only in so far as the occupation carries 
one into the low places mentioned. Trypanosomes 

1 in Sleeping 

At one time (1891) Manson advanced the idea sickness. 
that sleeping sickness is caused by the minute 
Filaria perstans. It has since developed that this 
parasite occurs in 70 per cent, of the natives in 
certain districts, and that sleeping sickness may 
occur in areas in which Filaria perstans does not 
exist; Manson has abandoned this view. A num- 
ber of investigators also found cocci in the cerebro- 
spinal fluid, but this occurred very rarely during 
life and at a late stage of the disease ; such organ- 
isms are probably secondary or agonal invasions 
in spite of their rather frequent occurrence. Fur- 
ther investigations by Castellani disclosed the pres- 
ence of a trypanosome (T. castellani) in the cere- 
brospinal fluid of a large percentage of the cases, 
and a little later Bruce found this organism in all 
the cases he had examined. This observation has 



488 



INFECTION AND IMMUNITY. 



been confirmed so many times that the trypan- 
osome is now generally considered as the cause of 
the disease. 
Tsetse Sleeping sickness is not contagious in the or- 
F, y« dinary sense, and Bruce furnishes rather strong 
evidence that it is transmitted by the bite of 
a tsetse-fly (Glossina palpalis). The distribu- 
tion of the disease corresponds to the habitat of 
this fly, and Bruce transferred the infection to 
monkeys by means of flies which had bitten those 
suffering from sleeping sickness. Sambon does 
not consider the experiments above criticism. 
Symptoms. A pronounced lethargy or somnolence is the 
most striking clinical feature of the disease. "The 
appearance of the somnolent condition is preceded, 
often for a long time, by prodromal signs, which 
are so characteristic that the patient's neighbors 
cannot possibly be deceived as to the fate that 
awaits him. The victim complains of weakness, 
langour, dejection, disinclination for work, head- 
aches, particularly localized over the occiput, a 
sensation of weight in the head and giddiness. 
His eyelids tend continually to close and he has a 
tendency to go to rest at unusual hours of the day ; 
for this purpose he seeks out lonely quiet spots, 
where he spends a long time in dozing" (Scheube) . 
For some time he is able to resist the somnolence, 
and when aroused gives intelligent answers. He 
eventually acquires an unsteady gait and walks 
about like a drunken man. The temperature of 
the body appears to be lowered, although irregular 
attacks of fever occur. The somnolence gradually 
becomes more intense, the patient grows very weak, 
the pulse small and thready, respiration difficult, 
the edema seen in trvansomatic fever is rather 



TRYPANOSOMIASIS. 



489 



constant, incontinence of the nrine and feces may 
develop; the patient commonly dies after passing 
into a state of deep stupor. Convulsions and pa- 
ralyses are noted; the mind usually is clear when 
the patient is conscious, although maniacal at- 
tacks and delusions are occasionally noted. The 
cervical and superficial lymphatics are frequently 
but not constantly enlarged. A papulo-vesicular 
eruption is quite characteristic and persistent and 
the skin becomes very dry. The incubation period 
varies from six to eighteen months, and the som- 
nolent state from three to twelve months. Eecov- 
ery rarely occurs. 

The essential anatomic change is meningo-en- 
cephalitis, the soft membranes being thickened, 
containing a milky fluid and the vessels of the pia 
and brain being surrounded by an extensive infil- 
tration of mononuclear leucocytes. 

The discovery of trypanosomes in sleeping sick- 
ness suggested that tryanosomatic fever may 
really represent the long prodromal stage of sleep- 
ing sickness. This view has been greatly strength- 
ened by a case reported by Manson in which a 
typical case of tryanosomatic fever was seen to 
pass into typical and fatal sleeping sickness. The 
wife of a missionary in upper Congo was bitten 
by a tsetse-fly, and following an inflammatory re- 
action at the seat of the bite, she developed and ran 
a long course of tryanosomatic fever. After a 
year and a half to two years of remittent attacks 
of fever, the organisms being found in the blood 
repeatedly, she grew weaker, became somnolent 
and died in a comatose condition. The anatomic 
changes at autopsy were typical of sleeping sick- 
ness. Some who are not quite willing to accept the 



Meningo- 

Encephalitis. 



Identity of Try- 
panosomatic 
Fever and 
Sleeping 
Sickness. 



Parasite. 



490 INFECTION AND IMMUNITY. 

unity of the two diseases suggest that the sleeping 
sickness may have been superimposed on trypano- 
matic fever. 

Assuming that the two conditions represent dif- 
ferent stages of the same disease, we would have 
to recognize trypanosomatic fever as the first stage 
and the lethargy of sleeping sickness as the second. 
If this proves to be correct the name of T. neprevi 
should be retained for the organism and the other 
names dropped (T. gambiense, T. liominis, T. 
castellani) . 

The It is believed that T. castellani is a distinct 
species of trypanosome. It is hardly possible to as- 
sociate it with nagana, since sleeping sickness and 
nagana do not coincide in their distribution, and, 
moreover, the morphology and pathogenicity of 
T. castellani differ from that of T. brucei. The 
former is not infectious for the "donkey, ox, 
guinea-pig, dog, pup, goat and sheep" (Euata). 
T. castellani is from 18 to 25 microns long and 2 
to 2.5 broad. Its morphology in general is like 
that of other trypanosomes, although there are 
sufficient differences to establish its independence. 
Its motility is rather slow, and in contrast to other 
trypanosomes it moves in the direction of its non- 
flagellated end. The failure to find any distinc- 
tive difference between this organism and 
T. neprevi (T. gambiense) is an additional point 
in favor of the unity of trypanosomiasis fever and 
sleeping sickness. 

TRYPANOSOMIASIS IN" ANIMALS. 
On account of the prevailing general interest in the 
subject, the more important trypanosomatic infections 
in animals and the corresponding parasites will be 
sketched briefly. 



TRYPANOSOMIASIS. 



491 



Musgrave and Clegg speak of certain general symp- 
toms which are common to surra, nagana, mal de cederas 
and dourine, as follows: "After an incubation period, 
which varies in the same class of animals and in those of 
different species as well as with the conditions of infec- 
tion, and during which the animal remains perfectly 
well, the first symptom to be noticed is a rise of tem- 
perature, and for some days a remittent or intermittent 
fever may be the only evidence of illness. Later on the 
animal becomes somewhat stupid; watery catarrhal dis- 
charges from the nose and eyes appear; the hair becomes 
somewhat roughened and falls out in places. Finally 
the catarrhal discharges become more profuse and the 
secretion more tenacious and even purulent; edema of 
the genitals and dependent parts appears; a staggering 
gait, particularly of the hind parts, comes on and is fol- 
lowed by death." 

The incubation period varies from a few to several 
days. Pronounced anemia develops, the method of de- 
struction of the erythrocytes being unknown. Lymphatic 
enlargement is the rule, and during the incubation period 
the parasites probably undergo great proliferation in the 
lymph glands. It is somewhat characteristic that mas- 
sive invasion of the blood stream occurs periodically. 
With a paryoxism of fever their numbers increase in the 
blood, and during the intermission they decrease and 
may be so few as not to be found microscopically. Even 
when few or no parasites are found in the circulation, 
however, the blood usually is infectious for other ani- 
mals. During the intermissions it is possible that they 
are largely within the lymph glands or other internal 
organs. The cause of these variations is not known, and 
it can not be said now that they are related to cycles of 
development like those of the malarial parasites. Voges 
suggests that they may represent the establishment of 
successive periods of temporary immunity (mal de 
cederas ) . These are only general features, and varia- 
tions occur in infections in different animals and by dif- 
ferent parasites. 

Trypanosoma lewisi, recognized in the blood of the rat 
by Lewis in 1879, and given its present name by Kent 
in 1882, infects wild rats throughout the world, and in 
some localities a very high percentage of the animals are 



General Symp- 
tomatology. 



Infectiousness 
of Blood. 



Trypanosomia- 
sis of Rats. 



492 INFECTION AND IMMUNITY. 

infected. The parasite is readily found in the peripheral 
blood (as from the tail), where a large number may be 
present in a single field of the microscope; sometimes, 
however, prolonged search is necessary for their discov- 
ery. Its dimensions vary: 1.4 to 3 microns in diameter, 
10 to 25 microns in length, according to different observ- 
ers. It is of lancet-form, possesses a finley granular endo- 
plasm and a clear ectoplasm, and from the latter spring 
the flagellum and the undulating membrane. "The for- 
mer (flagellum) is about as long as the body itself; 
it originates at the posterior end of the animal in a 
granule-like structure, called the flagellar root, extends 
forward as a marginal thickening of the undulating 
membrane and becomes free only at the anterior end of 
the animal from which it extends into the surrounding 
medium as a flagellum" (Doflein). At its posterior ex- 
tremity the parasite ends in a sharp point. In its an- 
terior portion it contains a strongly staining nucleus; a 
contractile vacuole is not described. Its motility is, per- 
haps, more active than that of any other trypanosome, 
and in a fresh mount of rat's blood it may move across 
the field so rapidly as to be followed with difficulty. 

Division takes place by longitudinal fission (rarely 
transverse), and by repeated division rosettes are 
formed. 
Cultivation. Novy and McNeal succeeded in cultivating this organ- 
ism artificially on a medium consisting of rabbit's blood, 
2 parts, agar, 1 part. The growth occurs in the con- 
densation fluid, and the organisms were carried through 
many generations. In cultures they vary greatly in size 
( from 1 to 60 microns in length ) . "The existence of the 
small forms accounts for the fact that we have repeat- 
edly been able to infect rats with Berkefeld filtrates of 
such cultures." It is remarkable that so many of the 
rats which harbor the parasites appear to be perfectly 
healthy. However, the animals not infrequently die 
from the infection, and in some instances fairly severe 
epidemics have been noted. The infection is found also 
in the hamster, a European rodent, and in white rats. 
White mice are susceptible to inoculation ( Doflein ) . 

Trypanosoma brucei, found by Bruce in 1894 in the 
blood of animals suffering from nagana or the tsetse-fly 
disease, in Zululand, is somewhat different morphologi- 






TRYPANOSOMIASIS. 493 

cally from T. leicisi, being more worm-like in form, hav- \ a gana. 
ing a blunt posterior extremity, less motility and greater 
pathogenicity. "The undulating membrane is broader 
and more plicate, the protoplasm colors more easily and 
more deeply" than in T. leicisi. Its length is said to 
vary, depending on the animal which harbors it, being 
largest in the rat and shorter and thicker in the dog. 
Its dimensions as given by Laveran and Mesnil are 1 to 
1% by 26 to 27 microns. Its structure is similar to that 
of T. leicisi, containing a nucleus near the middle of the 
body and a deeply staining centrosome in the posterior 
portion in or near which the flagellum has its origin. 
A contractile vacuole lies anterior to the centrosome. 

Natural infection (nagana) with this organism occurs 
in horses, cattle, mules, and also in some wild animals, 
as camels, buffaloes and hyenas. It is, however, a tropi- 
cal disease, occurring chiefly in various parts of South 
Africa. Xearly all animals are susceptible to artifi- 
cial infection by the injection of diseased blood. 

The distribution of nagana corresponds with the dis- Tsetse 
tribution of the tsetse-fly, and Bruce discovered that this Fly. 
fly, after feeding on the blood of an infected animal, 
transfers the disease to others by biting. Horses, asses, 
cattle and hogs were infected artificially in this way, but 
man appears not to be susceptible. It is assumed, but 
perhaps not definitely proved, that no other fly or insect 
transmits the disease. Immediately after it has fed on 
infected blood it is capable of transferring the disease; 
hence, further development of the parasite in the tsetse- 
fly is not essential for its continued infectiousness, and, 
indeed, it is not certain that any further development 
occurs. 

Nagana presents a remittent or intermittent type of 
fever, catarrhal secretion from the nose and eyes, sub- 
cutaneous edema, particularly of the abdominal region, 
prepuce and posterior extremities, roughening and shed- 
ding of the hair, marked emaciation, weakness and ane- 
mia develop, and the animal dies in a state of exhaus- 
tion. The spleen is greatly swollen, the red corpuscles 
are diminished in number, and the urine may be blood 
stained. The parasites are found in enormous numbers 
in the blood. 

The disease is almost invariably fatal. It may last 



494 



INFECTION AND IMMUNITY. 



for weeks or months in horses, and even much longer in 
eattle. It occurs not infrequently in epidemic form, 
wiping out the horses and cattle of infected regions. In 
wild animals it is suggested that the disease may be 
more chronic, and the shifting of such animals may 
serve to introduce the infection to new regions, but only 
to such regions as harbor the tsetse-fly. 
Cultivation. Novy and McNeal cultivate T. orucei on a medium 
similar to that used for T. lewisi. The former is more 
exacting in its conditions for growth, preferring a me- 
dium containing blood and agar in a ratio of two to one 
or three to one. Cultures were kept alive for at least 
one hundred days through eight generations, although 
virulence was soon lost. 
Surra. Trypanosoma evansi is the name given by Steele to a 
parasite discovered by Evans (1880), in India, in the 
blood of horses suffering from surra. It has the same 
general morphologic features as T. orucei, with dimen- 
sions of 1 to 3.5 or 4 microns by 20 to 35 microns, in- 
cluding the flagellum ( Musgrave and Clegg ) . It con- 
tains a nucleus and possibly a contractile vacuole. The 
whole posterior extremity is contractile, according to 
Musgrave and Clegg, and this may also be true of other 
trypanosomes. Its motility is moderate and eel-like. It 
differs from the trypanosome of rats {T. lewisi) in its 
larger diameter and in its greater pathogenicity; T. 
evansi is pathogenic for "nearly all animals." It is 
longer than T. orucei. 

Surra affects horses chiefly, and has caused immense 
losses in India and in the Philippine Islands. In India 
it is certainly transmitted by certain flies, and the same 
probably is true in the Philippines. Musgrave and Clegg 
demonstrated also that fleas may be of great importance 
as carriers. By this means they were able to transfer 
the disease from dog to dog, rat to rat, and rat to dog. 
They frequently found the parasites in native rats and 
believe that this animal may serve as a host in which the 
disease is maintained. Cattle are susceptible to infec- 
tion, but the disease is less malignant in them and runs 
a long course; hence, they may be an important factor 
in maintaining an epidemic. The disease is also trans- 
mitted from horse to horse. In India, camels, elephants 



TRYPANOSOMIASIS. 



495 



Dourine. 



and buffaloes also suffer from the disease. Surra resem- 
bles nagana in its clinical and anatomic aspects. 

Doflein gave the name of Trypanosoma equiperdum to 
an organism described by Eouget in horses and asses 
suffering from dourine. Laveran and Mesnil call it T. 
rougetii. According to Eouget, the parasite resembles 
T. brucei closely. Doflein (1901) states that a nucleus 
and vacuole have not been seen. Dourine occurs in 
Algiers, southern France, Navarre and in the Pyrenees 
districts of France and Spain. The infection is trans- 
mitted by coitus and is limited largely to animals which 
are used for breeding. Ulcerations, particularly of the 
genitals, are characteristic. That it is not transmitted 
by insects may be due to the absence of suitable insects 
from these localities. The identity of dourine with 
surra or nagana is not yet determined. It is said to be 
more chronic than surra. Doflein recognizes the organ- 
ism as an independent parasite. Infection may be trans- 
ferred to dogs, white mice and other animals. 

Trypanosoma equinum (Voges) or T. elmassianii is 
the parasite found in mal de cederas, a disease of horses 
in South America, resembling surra, nagana and dourine. 

Two different species have been found in the blood of 
South African cattle: T. theileri (Bruce, 1902) and T. 
transvaaliense (Laveran and Mesnil, 1902). The char- 
acteristic feature of the latter is the location of the 
centrosome near the nucleus near the center of the para- 
site. The following trypanosomes are found in fish: 
T. cobitis, T. carassii, T. remakii, T. solece, T. borrellii; 
the following in birds: T. avium, T. eberthii. T. balbianii 
occurs in oysters, T. rotatorium in frogs. 

Between various animals and the different try- immunity 
panosomes a number of examples of natural im- 
munity are known. The extent to which man is 
susceptible to sleeping sickness is not known, but 
since the disease may occur in Europeans as well 
as in native Africans, it is probable that suscepti- 
bility is general. Laveran and Mesnil state that 
sheep, deer and cattle which have recovered from 
nagana have an active immunity to the disease, 



Malde 
Cederas. 



Infections of 
Other Animals. 



496 INFECTION AND IMMUNITY. 

and it is thought that the immunity of some ani- 
mals (e. g.,-cow) may be increased by injecting 
infected blood. Koch, and also Schilling, have at- 
tempted to render trypanosomas suitable for vacci- 
nation by passing them through asses, and a cer- 
tain degree of success was reported. The serums 
of actively immunized animals do not exert a pro- 
nounced protective or curative action, although 
they may in some instances prolong the incubation 
period. Human serum has a certain protective 
and curative power for rats and mice which have 
been inoculated with the parasite of nagana. In 
some instances immune and normal serums kill 
trypanosomes, as shown by rapid loss of mobility. 
'Trypanroth." a most interesting bit of experimental therapy 
is that of Ehrlich and Sachs in curing and pro- 
tecting mice against mat de cederas by injecting 
and feeding "trypanroth," a synthetic dye. The 
dye was less efficient in experimental nagana and 
in trypanosomatic infections of rats, guinea-pigs 
and dogs. Among hundreds of other dye-stuffs 
no other was effective. The immunity and cure 
established in this way is ver}^ temporary and is 
to be referred to a reaction caused in the body 
rather than to a direct effect on the parasites.. The 
latter are not killed by the dye- in test-tube experi- 
ments. "One may conceive of the action of try- 
panroth in this way, that as a result of a fresh 
injection of the dye a reaction takes place in the 
animal's body, which leads to the death of the 
trypanosomes; the reaction products possess only 
a temporary character and cease to be formed as 
soon as the dye is disposed of." 

Laveran reports a favorable influence on try- 
panosomiasis in mice and rats by a combined treat- 
ment with sodium arsenite and "trypanroth." 



PYROPLASMOSIS. 497 

Spontaneous agglutination and agglutination by 
normal and immune serums have been described. 
At the present time agglutination is of no value 
from the standpoint of diagnosis. 

III. "'SPOTTED FEVER'"' OF THE ROCKY MOUNTAIN" 
STATES. 

In the valley of the Bitter Eoot Eiver of Mon- Limited 
tana, and in certain sections of Idaho, Wyoming 
and Washington an acute febrile disease, known 
in those localities as spotted fever, is encountered 
in the spring months. The disease is defined by 
Maxey as "an acute, endemic, non-contagious, but 
probably infectious, febrile disease, characterized 
clinically by a continuous moderately high fever, 
severe arthritic and muscular pains, and a pro- 
fuse petechial or purpural eruption in the skin, 
appearing first on the ankles, wrists and forehead, 
but rapidly spreading to all parts of the body." 
(Cited by Stiles.) 

In 1902-03, Wilson and Chowning studied many Pyropfasmtf 
cases of the disease in Montana, and described as Homn,s * 
the cause a protozoon organism which they con- 
sider as a pyroplasma (Pyroplasma hominis) . The 
organism is a hematozoon, occurring within the 
erythrocytes. Young cells resemble the "hyaline 
bodies" of malaria, are of ovoid shape, 1 micron 
thick and 1 to 2 microns long, and usually occur in 
pairs, but sometimes in numbers of 4 to 16, within 
an erythrocyte. The smaller ends of pairs often 
are directed toward each other, and they may be 
connected by a fine filament. They occur both in 
the red corpuscles and in the plasma. As they 
grow larger, two to three by three to five microns, 
only one parasite usually is found within an ery- 
throcyte, and in this stage they show active ame- 



498 



INFECTION AND IMMUNITY. 



Transmission 
by Ticks. 



Intermediate 
Host. 



boid movement with the formation of pseudopodia. 
Eventually they assume a spherical form in fresh 
preparations. They were able to transfer the in- 
fection to rabbits by the inoculation of infected 
blood. 

After identifying the organism as a pyroplasma 
and having in mind the part that ticks play in the 
transmission of Texas fever, and perhaps pyroplas- 
mosis in other animals (horse, sheep, dog), Wilson 
and Chowning directed their attention to the ques- 
tion of tick bites in those who become infected. 
It developed that of the 23 cases examined in 1903 
all had been bitten by ticks, and fourteen had been 
bitten in from two to eight days before the onset 
of the disease. They concluded that the disease is 
transmitted in this manner. 

They also searched for some other host than 
man, in which the parasites might nourish contin- 
uously and constitute a source of infection for the 
ticks. This they believe was found in a certain 
gopher (Spermophilus columbianus) . On the west 
side of the river — that side in which the disease 
attacks man — they found the erythrocytes of about 
20 per cent, of the gophers infected with a parasite 
similar to that found in man. On the other hand, 
the blood of sixty-two gophers from the uninfected 
side of the river showed no parasites. "Early in 
the spring the spermophile is said to harbor great 
numbers of ticks." Similar parasites were found 
in no other species of animals. 

Stiles, in later investigations, could not confirm 
the results of Wilson and Chowning, being unable 
either to find the parasites which they described in 
man, or to accept the tick-gopher hypothesis. Fur- 
ther investigation of this disease is needed. 



PYROPLASMOSIS. 



499 



The 
Parasite. 



TEXAS FEVER. 

Texas fever of cattle may be considered briefly as a 
well-established example of pyroplasmosis. 

Th. Smith and Kilbourne (1893) discovered a pear- 
shaped protozoon (Pyroplasma bovis) , which occurs in 
pairs in the erythrocytes of infected cattle. The para- 
site measures from 2 to 4 microns long by 1.5 to 2 
microns broad, the smaller ends of the pairs lying in 
apposition. The organisms have a rapid but rather coarse 
ameboid movement. About 1 per cent of the corpuscles 
are invaded ordinarily, but in fatal cases the proportion 
may rise from 5 to 10 per cent. The method of prolifera- 
tion of the parasite has not been followed out definitely. 
According to Smith and Kilbourne, numerous minute 
motile forms (coccus-like bodies) penetrate the corpus- 
cles and eventually reach the pear-shaped form. The 
breaking up of the adult pear-shaped parasites into such 
small forms has not been observed. 

A characteristic symptom of Texas fever is the pro- 
nounced hemoglobinuria which has given to the disease 
the additional name of hemoglobinuric fever. 

The disease is transmitted by means of a tick (Boophi- 
lus bovis ) . The six-legged larvae fill themselves with 
blood, and in about eight days have been changed into 
eight-legged nymphas. In eight days more they have 
changed into fully-formed sexual animals, and, after 
filling themselves with blood and after having been im- 
pregnated, they drop off the cattle and lay their eggs. 
The eggs in from 3 to 4 weeks have again grown into 
larvae, which are then ready to attach themselves to 
cattle ( cited from Kossel ) . Inasmuch as infected ticks 
transmit the parasites to their offspring, the bites of the 
larva? are able to give rise to the disease in cattle. A 
mature tick may deposit from 2,000 to 4,000 eggs. It 
has not been possible to transmit the disease to other 
species. 

The disease is endemic in the southwestern states, Transmission 
and the cattle in that region are supposed to acquire an 
immunity similar to that described by Koch in relation 
to malaria. Presumably the cattle first acquire the dis- 
ease when they are young, and those which withstand it 
show resistance to the infection in later life. Cattle 



Amebae. 



500 INFECTION AND IMMUNITY. 

from uninfected districts are more susceptible than those 
coming from localities in which the disease is endemic, 
and the latter even when apparently healthy may intro- 
duce the disease into new herds. This is done through 
transportation of the ticks. 

Partially successful attempts at active immunization 
have been made, and in Australia this is practiced on 
a fairly extensive scale. Five to ten cubic centimers of 
blood, taken from an infected animal, during the course 
of the disease or after recovery has been established, are 
injected into non-immune cattle. The disease is thereby 
reproduced in the latter with typical parasites in the 
blood. If the blood is taken from animals which have 
recovered, a milder infection results than when the blood 
of an actively infected animal is used (Pound, cited by 
Kossel ) . The resulting immunity is not an absolute one, 
however, and the percentage of mortality is fairly high. 
According to Dodson, the serum of animals which have 
completely recovered has no protective power for other 
animals. 

For prophylaxis it is important to free the cattle 
from ticks (as by an oil bath) and to avoid infected 
fields. If cattle are kept from an infected pasture for 
two years, the ticks die out very largely ( Morgan ) . 

IV. AMEBIC DYSENTERY. 

Amebse are unicellular animal organisms which 
contain one or more nuclei, a "contractile" vacuole, 
a granular endoplasm and a tougher more hyaline 
ectoplasm, having the power of locomotion by 
means of pseudopodia or by a gradual flowing for- 
ward of the cytoplasm. They nourish themselves 
by digesting bacteria and other lower organisms or 
solid particles of decaying matter, which they in- 
gest after the manner of phagocytes. They pro- 
liferate by division of an adult cell into two daugh- 
ter cells, and certain of them reach a cystic stage 
in which hundreds of endospores are formed 
(Ameba proteus). Some of them utilize higher 
animals as hosts only occasionally, while others 



AMEBIC DYSEXTERY 



501 



are known only as parasites. They frequently are 
encountered in the intestines of mice, frogs and 
other animals. 

Amebae are widely distributed in nature, exist- Distribution. 
ing to the depth of 2 meters in tropical soils, in 
the water of springs and wells and practically all 
surface waters (hot countries), and in stagnant or 
sluggish waters in higher altitudes. They exist on 
hay, fruits and vegetables of all kinds, especially 
those grown on or near the earth; e. g., beets and 
lettuce. 

Encystation takes place under certain unfavor- Resistance. 
able conditions, and in this condition the parasites 
withstand a temperature of — 15° C. for twenty- 
five da} T s (Musgrave and Clegg), and desiccation 
for ten to fifteen months. A temperature of 50° C. 
kills the vegetative and encysted forms. Sunlight 
for three hours and the a>ray kill them readily in 
the vegetative form, but not so readily when they 
are encysted. Most chemical bactericides destroy 
them, although they show a particular resistance to 
alkalies, even 20 per cent. XaOH (Frosch), and 
strong acids. They resist the action of 0.2 per 
cent. HC1, i. e., the acidity of the stomach con- 
tents. Quinin (1/2500 of the hydrochlorate) is 
strongly germicidal for Ameba coli. 

Under artificial conditions amebae proliferate Cultivation. 
in the presence of other micro-organisms, and 
suitable mixtures they may be kept alive in- 
definitely on slightly alkaline bouillon agar. 
The only condition in which amebae are found 
unassociated with bacteria is in the liver ab- 
scesses which occur as a complication of amebic 
dysentery. It is true that the bacteria may have 
been present originally, but in their absence it is 






502 



INFECTION AND IMMUNITY. 



supposed that enzymes normally present in the 
liver stimulate the growth and proliferation of the 
parasites. Amebae show a peculiar selective property 
for certain bacteria, although their affinities may 
be gradually modified. Ameba coli apparently pre- 
fers those organisms which flourish in the human 
intestines (B. coli, B. typhosus, Sp. cholera, Staph, 
pyog. aureus). Almost any strain will, however, 
grow with a variety of bacteria. Growth occurs 
only on the surface of the agar plates. When a 
pure strain of ameba is grown with a single species 
of bacterium the culture is spoken of as a "pure 
mixed culture." 

Amebic dysentery is primarily a disease of the 
tropics, where the natural conditions are favorable 
for the growth of the amebae and their conveyance 
to man. 

First found by Lambl (1860), then by Cunning- 
ham and Lewis (1870), the organisms were de- 
scribed more accurately and given the name of 
Ameba coli by Losch (1875). Losch recognized 
them as the cause of a chronic form of dysenter}^ 
but it was Kartulis, in particular, who found the 
amebae constantly in the discharges and ulcers of 
the disease, and also in the liver abscesses which 
accompany the infection. Since amebae demand 
the presence of living bacteria for their growth, 
Pathogenicity, their independent pathogenic nature has been ques- 
tioned by many who assume that the bacteria are 
the primary agents in causing the intestinal lesions 
and that the amebae are only incidental or second- 
ary factors. Many others, and particularly Mus- 
grave and Clegg, consider that amebae have essen- 
tial pathogenic properties and are the primary 
agents in producing amebic dysentery. By the 
feeding of encysted cultures grown with other or- 



Ameba 
Coli. 



AMEBIC DYSENTERY. 503 

ganisms, Musgrave and Clegg reproduced the dis- 
ease typically in many monkeys. In one instance 
the amebae were fed in conjunction with cholera 
vibrios; typical dysentery developed and during 
the course of the disease the vibrios disappeared 
from the stools. The vibrio alone proved to be 
non-pathogenic when fed to monkeys, and on this 
account they held the amebas to be the sole cause 
of the dysentery. 

The principal lesions occur in the large intes- Lesions 
tine, in which are found round or oval ulcers with 
infiltrated or undermined edges. The ulcers may 
increase in size, or coalesce with others, and cause 
the sloughing of large areas of the mucosa or even 
of the muscular coats. The organisms are found 
in the intestinal contents, on the surface of the 
ulcers, in the infiltrated base and edges, and in the 
underlying tissues. They have been found as- 
sociated with both chronic and acute appendi- 
citis. Amebic liver abscesses are not infrequent 
in those regions in which the disease is endemic. 
The organisms probably extend to the liver from 
the intestines through the lymphatic or portal 
vessels. Not infrequently the association of the 
amebae with bacteria is missed in the abscesses, 
and in these instances a "cold" abscess containing 
much necrotic material and detritus is produced. 
If contaminated with bacteria the abscesses have 
a more purulent character. 

Suitable prophylaxis against amebic infection is Prophyiaxii 
suggested by the known distribution of these or- 
ganisms. Of principal importance is the use of fil- 
tered or boiled waters and the avoidance of un- 
cooked vegetables in regions in which the disease 
is endemic, as in the Philippine Islands. 



504 INFECTION AND IMMUNITY. 

immunity. From the fact that foreigners going into tropical 
countries are more susceptible to infection than the 
natives, it is concluded that the latter have some 
natural (or acquired) immunity to the disease. 
Children are said to be less susceptible than adults 
and in them the disease yields to treatment more 
easily. There is no serum therapy for the infec- 
tions. The salts of quinin in strengths of 1-1500 
to 1-750 are amebicidal when injected into the 
colon. 

V. SARCOSPORIDIA. 

Morphology. Sarcosporidia are unicellular parasites which are 
found within the muscle cells of some animals, but 
very rarely in man. They are more or less tubular 
or oval in shape and are frequently referred to as 
Miescher's tubules. Their size varies greatly and 
certain species may reach a length of two centi- 
meters. When well developed they possess two 
capsules — a dense outer capsule, which is perfor- 
ated with minute canals (?) directed toward the 
center of the parasite, and an inner thin hyalin 
membrane. Both represent differentiated ecto- 
plasm (Doflein). The endoplasm, even in young 
cells, gives rise to numerous small nucleated 
spheres (pansporoblasts), which increase in size 
and each of which eventually becomes multinu- 
cleated and forms numerous kidney or sickle- 
shaped, nucleated sporoblasts. Each sporoblast 
finally gives rise or is changed into a well-charac- 
terized spore with a membrane and a nucleus. 
This process takes place first in the central part 
of the parasite, but eventually extends to the ends 
as well. The central part of the old parasites con- 
tains only the empty network of endoplasm, the 



8ARC0SP0RIDIA. 505 

spores having disappeared, and a section at this 
point strongly resembles that of a tubule. 

The parasites are nourished through osmosis. 
Xone of the forms have definite motility. When 
the parasite outgrows the muscle cell which con- 
tains it, it is freed and becomes an intercellular 
parasite. Bather vague references are made to 
tumor-like formation as a consequence. 

Sarcosporidia have been found only in verte- occurrence. 
brates, particularly in mammals; most often in 
sheep and hogs, but also in the horse, ox, mouse, 
rat. The muscles adjacent to the alimentary tract 
are involved principally (esophagus, intestines, 
diaphragm and abdominal muscles) and on this 
account it is supposed that infection takes place 
through the intestines. The exact method of in- 
oculation is not known. 

Sarcocystis lindemanni {Sarcocystis hominis or 
Gregarina lindemanni) is the only sarcosporidium 
definitely identified in man. The parasites were 
as large as 1.6 millimeters long and 170 microns 
broad. They possessed a thin capsule, thickened 
at the ends. The spores were banana-shaped and 
eight to nine microns long. The organisms were 
found in the muscles of the larynx. 

VI. BALANTIDIUM COLI. 

B. Coli is an infusorian (ciliate), with a more 
or less oval body, mouth opening and a short 
pharynx, is covered rather uniformly with short 
cilia, and presents longitudinal striations. It con- 
tains a bean-shaped chief nucleus and a secondary 
nucleus and two vacuoles on the right side. It meas- 
ures 70-100 microns in length and 50-70 in 
breadth. Proliferation is through simple division. 



506 , INFECTION AND IMMUNITY. 

Conjugation has been noted. Involution cysts are 
spherical and surrounded by a dense membrane. 
Pathogenic The parasite is found in the intestines of the hog 
Significance. as we -Q ag j n mail ^ an ^ £he f orme r may be its nor- 
mal host. It occurs also in sewage waters and has 
been found in drinking water. Infections have 
been noted in those having nothing to do with hogs. 
The organisms may reach the intestines of man in 
an encapsulated state (?). It is found in diar- 
rheal conditions in man rarely, and the question 
is still open as to whether the parasite is able to 
cause enteritis independently or whether it merely 
aggravates and prolongs an enteritis due to other 
causes. 

The cecum and colon show the principal changes 
at autopsy, and are of an inflammatory and ulcera- 
tive nature. 

A smaller species, B. minutum, has also been 
observed in the intestines of man. 

VII. CERCOMONAS INTESTINALIS. 

Morphology. This organism is small and colorless, the form 
spherical or oval. The single flagellum is for the 
most part very large and is situated at the anterior 
end (in the direction in which the parasite 
moves) ; the posterior end is long drawn out and 
is subject to changes in form. Sharp pseudopodia 
are sometimes formed. The nucleus lies in the 
anterior half of the body, and either here or on the 
sides are one or more vacuoles. A mouth opening 
is not differentiated, but at the base of the flagel- 
lum food is taken in at a particular point through 
a vacuole. Proliferation takes place through con- 
jugation, binary division and the formation of 
swarm spores ( ?) within encysted forms. They 
abound in fresh water and in infusions of grasses. 



TRICHOMONAS. 



507 



The}' are not of great parasitic importance, al- significance. 
though cercomonas has been found in the intes- 
tines, especially in inflammatory conditions (chol- 
era, typhoid), in pulmonary gangrene, putrid plu- 
ritis, and several forms have been observed in other 
animals. 

It is not yet certain that cercomonas may be an 
independent cause of enteritis. 



VIII. TRICHOMONAS. 

Eather small, of a general pear-shape, rounded 
or pointed anterior end, and possessing three or 
four long flagella. When only three flagella are 
present an undulating membrane surrounds the 
body like a spiral beginning at the base of the 
flagella and may prolong itself into a flagellum. 
The posterior extremity is moderately pointed, a 
nucleus lies in the anterior end, and toward the 
posterior are several non-contractile vacuoles. 
Methods of proliferation unknown (Doflein). 

Two species are found in man. Trichomonas 
vaginalis: possesses three flagella and an undu- 
lating membrane, and is of large size (15-25 mi- 
crons in length). It is found in the vaginal mu- 
cus, when of acid reaction, in a large percentage of 
women (Dolflein), particularly in vaginal catarrhs. 
It disappears in an alkaline reaction. 

Trichomonas hominis s. intestinalis : also pos- 
sesses three flagella and an undulating membrane, 
but is smaller than T. vaginalis. It is found as a 
parasite in the human intestines, particularly in 
diarrheas (typhoid, cholera, mucous colitis, etc.,) 
and inhabits especially the upper and middle por- 
tions of the intestines. It is evacuated in consid- 
eral numbers following administration of cathar- 
tics. It appears not to be of much pathogenic sig- 



Morphology. 



Species. 



508 INFECTION AND IMMUNITY. 

nificance, but finds in the liquid stools and in an 
alkaline reaction conditions which favor its prolif- 
eration. It may be transmitted as a contagion 
(Epstein). 
other Other species of trichomonas occur in the intes- 
tmes 01 different animals. 

Other less important flagellates are: Lamblia 
intestinalis, found in the intestines of many ani- 
mals and in man in Germany, Italy, Eussia and 
Sweden; Bodo urinarius (Cystomonas urinarius, 
Plagiomonas urinaria), found in the urine in cys- 
titis (Kiinstler). 

IX. COCCIDIOSIS. 

Coccidia are essentially cell parasites, preferring 
the epithelial cells of the intestines and liver, al- 
though they may be carried to other organs. They 
have an alternating asexual and sexual cycle of 
development. The young sickle-shaped and nu- 
cleated sporozoite penetrates an epithelial cell, 
grows in size, and the nucleus subdivides many 
times to form new young cells, which eventually 
escape again as sickle-shaped sporozoites. This 
asexual process is called schizogony. Several stages 
of schizogony may follow successively, but event- 
ually the organisms lose their proliferative power 
unless they are fortified by a sexual cycle. In the 
sexual cycle (sporogony) some of the sporozoites 
become differentiated into larger granular cells 
(female) and others into smaller cells (male). 
Of these two cells the male eventually divides into 
many flagellated microgametes, each of which is 
able to penetrate and fertilize a female cell (macro- 
gamete). The female cell then forms a capsule, 
becomes an oocyst, divides into sporoblasts, each 
of which eventually forms sickle-shaped spores, 



Life Cycles. 



COCCIDIOSIS. 509 

which when liberated are again called sporozoites. Species. 
Several species are recognized, depending on the 
nnmber of spores formed by the oocyst. In some 
instances the spore formation takes place in the 
outer world, and when the oocysts are ingested the 
sporozoites are liberated. 

Coccidium cuniculi s. oviforme is a frequent 
parasite in the intestines and liver of the rabbit, 
occurs occasionally in the same organs in man from 
association with rabbits (?), and causes a hemor- 
rhagic dysentery in the cattle of some countries 
(Switzerland). Horses, goats and swine may also 
be infected. 

Spore formation takes place outside the host. 
The oocyst is discharged in the feces and produces 
four spores, each of which forms two sporozoites. 
A new host is infected by the ingestion of spores. 

Diarrhea and emaciation result from infection Results of 
of the intestines, and in the liver cheesy nodules ,nfectio "- 
(coccidia nodules) are formed, containing para- 
sites, degenerated cells and proliferated epithe- 
lium. A papillomatous proliferation of the epi- 
thelium of the bile passages and intestines may be 
produced. 

Coccidium bigeminum, a coccidium in which 
the oocyst divides into two spore-containing cysts, 
has been found in man several times. 



GROUP VI. DISEASES OF DOUBTFUL OR 
UNKNOWN ETIOLOGY. 



Negri. 



I. HYDROPHOBIA. 

Following the investigations of Pasteur, in 
which it was found that the virus of hydrophobia 
exists in the central nervous* system in pure cul- 
ture, the conditions seemed favorable for the dis- 
covery of the specific agent. As in the case of 
many other diseases, various bacilli, cocci, yeasts 
and so-called protozoa have been described as the 
cause, but satisfactory proof of their etiologic role 
has not been provided. 
Bodies of Among the recently described parasites (?) cer- 
tain protozoon-like bodies (Negri bodies) found 
by Negri in the ganglionic cells are of a suggestive 
nature. Their average diameter is about five mi- 
crons, but it varies between one and twenty-seven 
microns. They possess a "round, oval, elliptical, 
or coarse triangular form" (Marx), are differen- 
tiated into a central granular and a peripheral 
structure and may be surrounded by a doubly- 
contoured membrane. Negri considers these bod- 
ies specific for hydrophobia and reliable as a basis 
for anatomic diagnosis. They are found particu- 
larly in the pyramidal cells in the cornu Ammonis, 
the cells of Purkinje in the cerebellum, and the 
large cells of the cerebral convolutions. Many oth- 
ers have confirmed the findings of Negri. Against 
the hypothesis that these bodies are the cause of 
hydrophobia, the following points are cited : The 
distribution of the Negri bodies does not corre- 
spond with the greatest concentration of the virus 



HYDROPHOBIA. 511 

in the nervous tissue, the latter being most abun- 
dant in the medulla and pons where the Negri 
bodies are encountered rarely. They are not found 
invariably in animals dying of hydrophobia. They 
present certain analogies with "protoplasmic in- 
clusions" seen in other conditions, as in carcinoma, 
variola, etc. Eemlinger found that the virus 
passes through appropriate Berkefeld filters, and 
for this reason Schiider holds that the bodies of 
Negri, being too large for filtration, can not be 
considered as the specific organism. The view of 
Schiider may be criticized, since the smallest 
Negri bodies are so minute that their filtration 
would seem to be possible. Nevertheless, it must 
remain doubtful whether bodies one micron in di- 
ameter, the proliferation of which has not been 
proved, may be considered as parasites. The hy- 
pothesis of Negri is hardly on a satisfactory basis 
at present. Eemlinger considers the bodies as 
"involution forms" of the tissue cells which have 
been invaded by the true parasite. 

The fllterability of the virus argues for its mi- FHterabMty 
croscopic size. By means of filtration one may 
isolate it even from brains which are badly decom- 
posed, and the method renders it possible to ob- 
tain pure cultures for purposes of immunization. 
Inoculation with filtered virus is sometimes fol- 
lowed by a prolonged incubation period which may 
depend on the retention of many of the organisms 
by the filter. A similar effect was produced by 
Hogyes by inoculating with diluted virus. 

By prolonged centrifugation of an emulsion of 
infected nervous tissue the overlying fluid loses its 
infectiousness. 

The possibility that the organism secretes a sol- 



of Virus. 



512 INFECTION AND IMMUNITY. 

Toxin, uble toxin is important from the standpoint of im- 
munization. A number of observers, particularly 
Babes, and Heller and Bertarelli, noted that fil- 
trates of infected nervous tissue sometimes cause 
emaciation, paralyses and eventual death without 
producing a disease which is transmissible to other 
animals. The organism is without doubt toxic, 
but these results give us no idea of the nature of 
the toxin. 
Resistance The virus of hydrophobia as contained in the 
central nervous system of infected animals exhib- 
its strong resistance to chemical germicides. Five 
per cent, carbolic acid destroys it in fifty minutes, 
1 per cent, in three hours, and 1-1000 corrosive 
sublimate in three hours (Marx). It resists the 
action of putrefactive bacteria, and has been found 
virulent in animals which had been buried for two 
to four weeks, even when the brain was putrid. Di- 
rect sunlight destroys it, however, in a very short 
time. According to Tizzoni and Bongiovanni, the 
rays of radium have a destructive action on the 
virus. It is less resistant to heat, being destroyed in 
one-half hour at a temperature of 52-58° C. 
(Hogyes), but is not affected by the temperature 
of liquid air for three months. Chlorin destroys 
it very rapidly. It is gradually weakened by 
desiccation, as first shown by Pasteur, the virus 
probably undergoing gradual death rather than 
mere attenuation. It is said to be attenuated by 
the action of the gastric juice and by the bile. 
When the nervous tissue is emulsified in glycerin, 
virulence is retained for months (Eoux). On the 
other hand, glycerin appears to destroy the viru- 
lence of filtrates (Di Vestea). 

Pasteur gave the name of street virus (virus 



HYDROPHOBIA. 



513 



Low Virulence 
of Fixed Virus 
for Man. 



de rue) to that obtained from the nervous tissue of JfJJJand 
dogs in which the disease develops spontaneously. Fixed virus 
When the street virus is injected subdurally into 
the rabbit the latter develops hydrophobia only 
after an incubation period of from two to three 
weeks. If, however, this virus is passed from one 
rabbit to another, its virulence gradually increases 
until the incubation period decreases to six days. 

At this point it is called fixed virus (virus fixe), 
and its virulence can not be further increased. 
Passage through the cat, fox and wolf also in- 
creases virulence. On the other hand, by passing 
it repeatedly through the monkey (Pasteur), the 
chicken (Kraus) or the dog it becomes attenuated 
for the rabbit and virulence may be lost entirely. 

Although virus fixe represents its highest degree 
of virulence for rabbits, there is good reason for 
believing that repeated passage through the rab- 
bit decreases the virulence of the virus for man. 
In other words, street virus is more infectious for 
man than fixed virus. This may to some extent ac- 
count for the success of the Pasteur treatment. 
Ferran, indeed, uses unaltered virus fixe for the 
protective inoculation of man. 

By means of inoculation experiments the virus 
may be demonstrated invariably in the brain, 
spinal cord, and usually in the salivary glands and 
saliva of animals which have died of the disease. 
These tissues are specifically affected, and the virus 
probably proliferates in them. By one or another 
observer its presence in the following organs and 
excretions has been demonstrated: Suprarenal 
gland, lachrymal gland, vitreous humor, urine, tes- 
ticular secretion, lymph, milk, in the peripheral 
nerves and cerbrospinal fluid. Marx states that 



Distribution of 
Virus in the 
Body. 



514 INFECTION AND IMMUNITY. 

it lias not been found in the liver, spleen, blood and 
aqueous humor. Courmont and Nicolas found it, 
however, in the aqueous humor of rabbits after 
death. The possibility of postmortem invasion of 
this fluid has been suggested. It has been found 
occasionally in human saliva during life, and at 
the site of the wound following death (Pace). 
Means of Hydrophobia is transmitted almost exclusively 
by the bites of infected animals, the virus being 
conveyed in the saliva. Accidental inoculation may 
occur in handling infected tissues. The virus does 
not penetrate the intact skin, and it is customary to 
consider a bite as harmless unless the continuity 
of the skin is broken. Experimentally, infection 
has been caused by placing the virus on the mu- 
cous membranes of the conjunctiva, nose and 
mouth, in the absence of discernible lesions. Pace 
mentions a man who contracted the disease after 
his rabid dog had inserted the tip of its tongue in 
his (the patient's) nose. But one authentic ex- 
ample of transmission from man to man is found 
in medical literature. This occurred through kiss- 
ing or biting, during coitus. In rare instances it 
seems to have been transmitted from the mother 
to the fetus in rabbits. 

The dog is the most common carrier of hydro- 
phobia. In some countries (Eussia, Hungary) rabid 
wolves cause many infections. The disease has been 
conveyed by the bite of the cat, mouse and horse, 
and possibly by the skunk in some of our western 
states. The dog is, however, the natural host of 
the parasite, and either by his bite or by experi- 
mental inoculation practically all animals, at least 
mammalians, may be infected. 

The incubation period in animals varies from 



HYDROPHOBIA. 515 

two weeks to several months. In man it varies incubation 

Period* 

between twenty and sixty days usually, but may be 
as short as seven or ten days, or as long as twenty 
months (rare). In children it is shorter than in 
adults. The location of the bite is also of impor- 
tance in determining the length of incubation. It 
is shortest following wounds of the head and neck, 
somewhat longer when the injury is in the hand or 
arm, and still longer when in other parts of the 
body. The degree of laceration is also a factor, de- 
pending possibly on the introduction of larger 
quantities of virus, and on larger surfaces for its 
absorption. The bite of the wolf is said to be most 
virulent, and next in virulence is the bite of the 
cat and dog. 

Not all who are bitten by rabid animals develop 
hydrophobia. Correct figures on this point are dif- 
ficult to obtain, since in many instances the ani- 
mals are only suspected of being rabid. According 
to Hogyes, 15 to 16 per cent, of those who are bit- 
ten contract hydrophobia. The percentage is much 
higher following bites by the wolf. The disease is 
invariably fatal to man. 

The symptoms of hydrophobia in man differ in 
no essential respects from those seen in animals. 

The immediate determination of hydrophobia Diagnosis 
in dogs which have bitten man is of the greatest 
importance. In many instances the behavior of the 
animal is sufficiently characteristic to justify clin- 
ical diagnosis of the disease. The disposition of 
the animal changes suddenly, it ceases to play, eats 
various indigestible substances, as glass, iron and 
wood, utters pathognomonic ( ?) long-drawn-out 
howls, may become ferocious, or, on the other 
hand, quiet and sullen. At autopsy the meninges 



in Dogs. 



516 INFECTION AND IMMUNITY. 

and nervous tissue are congested if the disease is 
advanced, and the indigestible mentioned sub- 
stances may be found in the stomach, although the 
latter finding has little or no diagnostic importance. 
so-caiied a number of histologic changes have been de- 
Lesions, scribed as characteristic. Among these are the 
bodies of Negri, described above. Eemlinger at- 
taches a great deal of importance to them as a 
means of diagnosis. Babes describes perivascular 
nodules of lymphoid cells (Wutknotchen) in the 
medulla and cord. The lesion of Van Gehuchten 
consists of a proliferation of the endothelial cells 
(neuronophages) surrounding the ganglionic cells, 
the latter at the same time undergoing atrophic 
and degenerative changes. This change is most 
marked in the cervical ganglia. One group of ob- 
servers finds these lesions constant in animals 
which have died of hydrophobia, but they may be 
absent if the animal is killed during the course of 
the disease; hence their absence does not exclude 
the diagnosis of hydrophobia. Others have found 
similar changes in other diseases. Metchnikoff, 
. it will be remembered, observed the destruction of 
ganglionic cells, by neuronophages in aged dogs 
(page 179). 

We are hardly able at present to consider these 
changes as pathognomonic. Particularly in early 
stages of the disease they may be absent. The bite 
of a rabid dog is infectious in from two to four 
days in advance of the development of symptoms, 
and autopsy performed at this time may show 
neither gross nor microscopic changes which are 
characteristic. In communities in which hydro- 
phobia is known to be endemic, all cases of dog bite 
accompanied by penetration of the skin should re- 
ceive the Pasteur treatment. 



HYDROPHOBIA. 



517 



A great deal of experimental work which can not Extension 
be given in detail shows conclusively that the virus Nerves. 
is conveyed to the central nervous system by means 
of the peripheral nerves. The conditions then are 
similar to those in tetanus with this exception : In 
hydrophobia the living virus reaches the central 
nervous system, whereas in tetanus the bacilli re- 
main at the site of the wound. This condition ex- 
plains the shorter incubation period in hydropho- 
bia, as in tetanus, when the infection atrium is 
near the central nervous system (e. g., face). When 
the infection is introduced into any particular 
part of the body surface, the virus is first demon- 
strable in the corresponding segment of the cen- 
tral nervous system. Although transmission by 
the nerves is the rule, infection may be accom- 
plished in rabbits by intravascular injection. On 
the whole, however, infection is closely associated 
with the wounding of nerves. It has indeed 
been shown that if wounding of nerves is entirely 
avoided, as in intraperitoneal injections into rab- 
bits (Marx) the full virulent nervous tissue may 
be used for immunization. A single injection of a 
large quantity brought about immunity in twelve 
days. 

The muzzling of dogs is a general prophylactic Prophylaxis. 
measure, which should be enforced in communities 
in which hydrophobia is known to occur. No mat- 
ter how thoroughly the cauterization and antisep- 
tic treatment of wounds is carried out it can in no 
ease be depended on to destroy the virus. Even 
within five minutes the virus may be carried to a 
point which is beyond the reach of the cautery. In 
spite of this fact, however, cauterization should 
not be neglecterl, even when the Pasteur treatment 



518 



INFECTION AND IMMUNITY. 



can be instituted at once. The greater the quantity 
of virus introduced by the bite the shorter will be 
the incubation period, and there is good reason to 
believe that cauterization (actual cautery) prop- 
erly carried out destroys a sufficient amount of 
virus to prolong the incubation period. A long 
incubation period is greatly in favor of the success 
of the Pasteur treatment. 
Preparation of Pasteur's first protective inoculations were car- 
v,r t U eur°Treat- ried out with virus which had been attenuated by 
ment * passage through the monkey. The virus fixe ob- 
tained from the rabbit, as- described above, was 
soon substituted for that of the monkey. In order 
that an antirabic institute may continuously have 
on hand a sufficient amount of vaccine, it is neces- 
sary to inoculate two or three rabbits daily. For 
this purpose an emulsion of the medulla of a rab- 
bit which has died of hydrophobia is inoculated be- 
neath the dura mater. A short time before the 
animals would die of the disease, they are killed 
by bleeding, and the spinal cords removed with all 
possible precautions for asepsis. Each cord is cut 
into two parts and each part suspended in a prop- 
erly constructed jar which contains solid potas- 
sium hydrate. After the jar is sealed desiccation 
is allowed to proceed for fourteen days, at the end 
of which time the infectiousness of the tissue has 
so decreased that it is suitable for the first injec- 
tion. The vaccine should be free from bacteria. 

As is well known, the Pasteur prophylactic 
treatment consists of the subcutaneous injection 
on successive days, of suitable quantities of virus 
fixe, prepared as described above, beginning with 
the cord which has been desiccated for fourteen 
days and gradually using fresher cords until viru- 



Technic of 
Treatment. 



HYDROPHOBIA. 519 

lent virus has been inoculated. The vaccine is pre- 
pared for use by emulsifying one centimeter of a 
cord in 5 c.c. of salt solution or some "artificial 
serum," and in a single treatment from 1 to 3 c.c. 
of this emulsion is injected, usually into the sub- 
cutaneous tissue of the anterior abdominal wall. 
In this region there is less likelihood of injuring 
large nerves, and local complications, which, how- 
ever, occur rarely, are of less consequence. 

The rapidity with which one should pass from 
the fourteen-day cord to fresh virus depends on the 
urgency of the case. When there is good reason to 
suspect a short incubation period, or when some 
days have followed the bite an "intensive" treat- 
ment should be used ; in other cases the progression 
may be slower. The following conditions augur 
a short incubation period: Bites of children, who 
are more susceptible than adults, and in whom 
the injuries usually are on the face; bites on the 
face and neck in all cases; lacerated wounds in 
which there is a larger surface for absorption of 
the virus. The influence which proper cauteriza- 
tion exerts on the incubation period was mentioned 
above. 

The table on page 520, taken from Marx, illus- 
trates a "light" and an "intensive" treatment. 

This scheme is variously modified in different 
institutes, especially in the direction of a more 
rapid progression to virulent material. 

Other methods of attentuation are also used, as gJJ^ 
the following: Heating emulsions of fresh virus Attenuation. 
at 58° C. for different lengths of time, or at dif- 
ferent temperatures (80° to 30° C.) for ten min- 
utes (Babes-Puscari) ; digestion of virus with nat- 
ural or artificial gastric juice (Tizzoni and Cen- 



520 



INFECTION AND IMMUNITY. 



tanni) ; the use of fresh but very dilute virus 
(Hogyes). Ferran, in Barcelona, inoculates man 
with the fresh unaltered virus fixe, and in nearly 
2,000 cases but two cases of hydrophobia devel- 
oped. This indicates clearly the low infectious- 
ness of virus fixe for man. 



Light. 


Intensive. 


Day of 


Age of 


Amount of 


Day of 


Age of 


Amount of 


Treat- 


Dried Cord 


Emulsion 


Treat- 


Dried Cord 


Emulsion 


ment. 


in Days. 


Injected. 


ment. 


in Days. 


Injected. 


1 


. 


14 


3 






ru 


3 


13 


3 


1 




13 


3 


2 




12 


3 




12 


3 




11 


3 






JL1 


3 


3 




10 


3 






rio 


3 




9 


3 


g 




9 


3 


4 




8 


3 


" 


" 


8 


3 


7 


3 






I 7 


3 


5 




I 


2 

9 


3 


• 


2 


2 
2 


6 


5 


2 


4 


5 


2 


7 


5 


2 


5 


5 


2 


8 


4 


2 


6 


4 


2 


9 


3 


1 


7 


3 


1 


10 


5 


2 


8 


4 


2 


11 


5 


2 


9 


3 


1 


12 


4 


2 


10 


5 


2 


13 


4 


2 


11 


5 


2 


14 


3 


2 


12 


4 


9 


15 


3 


2 


.13 


4 


2 


16 


5 


2 


14 


3 


2 


17 


4 


2 


15 


3 


2 


18 


3 


2 


16 


5 


2 








17 


4 


2 








18 


3 


2 








19 


5 


2 








20 


4 


2 








21 


3 


2 



It seems unnecessary at this date to quote sta- 
tistics to show the value of the Pasteur treatment. 
Observations indicate that immunity is not fully 
established until about fourteen days after the 
completion of the treatment, and in a certain num- 
ber of cases the disease develops before this time 
has passed. The number of deaths after this pe- 
riod is exceedingly small and has grown less with 



HYDROPHOBIA. 521 

improved teclmic. In 1886 the number of deaths 
which occurred after fifteen clays had passed 
amounted to 0.94 per cent.; in 1902 to 0.18 per 
cent. 

The immunity established by the Pasteur treat- immunity and 
ment is, in all probability, antimicrobic in nature, ertfes. r ° P " 
The serum of both man and animals, after immun- 
ization, is able to destroy the infectiousness of rabic 
nervous tissue, i. e., the serum is rabicidal (Babes 
and Lepp, 1889). The technic of Kraus and 
his co-laborers is well adapted to show the rabi- 
cidal properties of the immune serum. Eabid ner- 
vous tissue is made into an emulsion with salt 
solution in a dilution of 1-100, and then filtered 
through paper to remove coarse particles of tissue. 
To quantities of 0.5 to 1.0 c.c. of this emulsion 
varying amounts of fresh immune serum are added, 
and after eighteen hours' contact the mixtures are 
injected into rabbits to determine the degree of 
infectiousness. Small quantities of rabicidal sub- 
stance may be detected in this way. 

Natural resistance to hydrophobia does not go 
hand in hand with the antirabic power of an ani- 
mal's serum. Old pigeons, for example, develop the 
disease following intracerebral injection of the 
virus, although their serum is not rabicidal. 

Babes and Lepp also showed that the immune 
serum has protective powers which are analogous 
in their efficiency with those of bactericidal serums. 
Babes advocates and practices the mixed method 
of immunization in severe cases, immune serum be- 
ing injected in addition to the virus. The serum 
has little or no curative value. 



522 



INFECTION AND IMMUNITY. 



Hypothetical 
Causes. 



Transmission 
to Monkeys. 



II. SYPHILIS. 

It is impossible in this place to describe or even 
mention the many cocci, bacteria and protozoa (?) 
which have been brought into etiologic relationship 
with syphilis. Until very recent times the bacil- 
lus of Lustgarten (Bacillus syphilis (?) ), occu- 
pied a fairly prominent position as the possible 
cause. This organism resembles the tubercle bacil- 
lus in its morphology and staining properties, and 
is not to be differentiated from one of the smegma 
bacilli. Its recognition in syphilitic lesions has 
always been difficult, and by far the greatest num- 
ber of investigators have been unable to demon- 
strate it. It has never received general recognition 
as the cause of the disease, and its presence in le- 
sions of the genitals has no significance because of 
the occurrence of smegma bacilli in this locality. 

The bacillus of De Lisle and Julien, and that 
of Joseph and Piorkowski rest on no better basis. 

Two important discoveries of recent date lend 
to the hope that some light may be thrown on many 
dark problems in relation to syphilis. 

The first has to do with the transmission of the 
disease to lower animals. Such attempts have 
been very numerous, both by the inoculation of 
syphilitic tissues and of organisms cultivated from 
the tissues. We have not the space to describe in- 
dividual experiments, and can only say that trans- 
mission to various animals (monkey, guinea-pig, 
rabbit, hog, etc.) has been claimed in a number of 
instances. 

Leaving the monkey out of consideration, it 
is reasonably certain that none of these reported 
successes represented the production of syphilis; 
this is shown decisively by experiments published 



SYPHILID. 



523 



by Xeisser in 1902. This may not be true, how- 
ever, in regard to the inoculation of monkeys, in 
which successful experiments were reported by 
Klebs (1879), Martineau and Hamonic (1882) 
and Sperk (1886-8).* It is quite likely that Sperk, 
in particular, accomplished transmission several 
times. However, the successes were not uniform, 
and the possibility of such transmission has become 
an assured fact only in the most recent times. 

It occurred to Metchnikon 3 and Koux as it had 
occurred to others that the monke}^, particularly 
the higher species (chimpanzees), should on ac- 
count of their biologic proximity to man, be the 
most suitable animal for the production of experi- 
mental syphilis. Attention has already been called 
to this proximity as indicated by the reaction of 
serum precipitins. 

Their first inoculation was performed on a fe- 
male chimpanzee, virus from a primary lesion and 
from mucous patches being introduced by means 
of scarification into the prepuce of the clitoris and 
into the skin of the eyebrow. The wounds healed, 
and twenty-six days after inoculation a vesicle 
which soon was surrounded by induration appeared 
on the prepuce. This lesion was pronounced a typi- 
cal hard chancre by eminent dermatologists and 
sy philologists. With the appearance of the chan- 
cre the inguinal lymph glands became enlarged 
and one month later a papular eruption appeared 
on the thighs, abdomen and back. The papules 
persisted for more than a month, and were still 
discernible when the animal died several weeks 
later of pneumococcus infection. Before this ani- 



Experiments of 
Metchnikoff 
and Roux. 



Transmission 
from Monkey 
to Monkey. 



Flexner : "The Etiology of Syphilis," Med. News, Dec. 9, 



1905. 



524 INFECTION AND IMMUNITY. 

mal died a second chimpanzee was inoculated from 
the primary and secondary lesions of the first ani- 
mal, resulting in the development of primary le- 
sions and of adenitis. Still another successful in- 
oculation resulted in secondary lesions with the 
formation of mucous plaques. They have since 
performed many similar experiments with positive 
results, when the higher types of monkeys were 
used. Confirmation has come from a number of 
independent experimenters (e. g., Lassar, A. Neis- 
ser, Kraus, Mexner), and A. Neisser in particular 
has taken up the work on an extensive scale. 
Experiments Some of . Neisser's work is of the utmost impor- 
tance. The experiments of Metchnikoff and Eoux 
had already indicated that the higher monkeys 
(chimpanzee, etc.) acquired generalized syphilis 
more readily than the lower species. Neisser's 
work corroborates this, and he recognizes a scale of 
susceptibility which corresponds roughly with the 
proximity of the different species to man, as indi- 
cated by general morphology and the reaction of 
serum precipitins. The chimpanzee, orang-utan 
and gorilla are the most susceptible, and the syph- 
ilis produced in them approaches closely that seen 
in man, including the secondary symptoms. It is 
suspected that the cynocephalus varieties are less, 
and the macacus varieties least susceptible. Among 
the macaci the smaller types (rhesus) are more 
resistant than the larger. The lower susceptibility 
of these animals is recognized by the failure of 
secondary symptoms to develop, hence in them the 
syphilis may be purely local (Neisser). The study 
of experimental syphilis is so young that generali- 
zations at this time are out of the question. 
A second discovery of no le?s importance was 



SYPHILIS. 525 

that of a spirocheta* (Spirochetes pallida) in the spirochete 
primary and secondary lesions of syphilis by Hoff- possible cause. 
niann and Schaudinn in 1905. "The organism 
measures from 4 to 10 microns in length, the aver- 
age being about that of the erythrocyte of man. 
Its width varies from immeasurable thinness to 
one-half micron. It possesses from three to twelve, 
sometimes more, curves, which are sharp and reg- 
ular and resemble the curves of a corkscrew. The 
poles are sharpened. The organism is mobile, and 
the motions consist of rotations on the long axis, 
forward and backward movements, and the bend- 
ing of the entire body. Flagella have not been 
seen" (Flexner). It may be stained by the azur 
of Giemsa or the Eomanowsky stain or some one of 
its modifications. Confirmation has come from a 
large number of observers in rapid succession, 
little difficulty being found in demonstrating the 
spirals in preparations from chancres and mucous 
plaques, secondary lesions in the skin and in Distribution 
fluid aspirated from the lymph glands which are 
regional to the chancre. Schaudinn found it once 
in fluid aspirated from the spleen, but its demon- 
stration in the blood has been accomplished in only 
a few instances after prolonged centrifugation of 
the blood. Levaditi and Petresco discovered it 
in the fluid of an artificially produced blister. Two 
additional facts make the case of Spirocheta pal- 
lida a strong one, i. e., its occurrence in the lesions 
of the congenitally syphilitic and in the experi- 
mental lesions of the monkey, even when the inoc- 

* The discovery of spirochete in yaws, by Castellanl and 
by Wollman, is a very suggestive one, in view of the tend- 
ency in many quarters to considers yaws as a manifestation 
of syphilis. 



of Spirocheta. 



526 



INFECTION AND IMMUNITY. 



Infection. 



Occurrence 
of Virus. 



ulation is made from a previously infected monkey 
(Kraus). Knowledge concerning its relation to 
tertiary lesions is not yet of a satisfactory nature. 

Suggestive as these results are, we must appre- 
ciate that much remains to be learned before the 
causal relationship of Spirocheta pallida to syphilis 
can be an unquestioned one. 

Infection usually is venereal. It is not defi- 
nitely known whether a defect of the surface of the 
prepuce, glans, vagina, etc., is essential for infec- 
tion. The epithelium in these localities is so deli- 
cate that defects of microscopic dimensions may be 
easily produced, and infection may take place 
through such defects as through grosser lesions. It 
is well known that the lip, tongue, conjunctiva and 
finger may be the seats of primary lesions, and it 
is probable that no part of the body surface is 
immune when the virus is introduced suitably. 

The secretions of all surface lesions in syphilis 
are infectious, except those of gummata. Concern- 
ing the infectiousness of different normal secre- 
tions and the situation of the virus in internal or- 
gans, we may look forward to more positive infor- 
mation than we have had hitherto. Defibrinated 
blood and serum from cases of secondary syphilis 
did not produce lesions when injected subcuta- 
neously and intraperitoneally into monkeys (Neis- 
ser). Neisser had previously performed experi- 
ments on man which showed the serum not to be 
infectious. We can not conclude from these results, 
however, that the blood in syphilis is not infected. 
Inoculations into monkeys from the internal or- 
gans (liver, spleen, bone marrow) of syphilitic 
monkeys, gave negative results. The virus is non- 
filterable, i. e., it is so large or its form is such 
that it does not pass through a Berkefeld filter. 



SYPHILIS. 



527 



Clinical experience indicates that the virulence virulence. 
of the syphilitic virus is not uniform. It is pos- 
sible that certain strains are more likely to bring 
about "post-syphilitic" diseases than others. That 
the resistance of the virus outside the body is low 
seems evident from the fact that transmission is 
practically unknown except as it occurs by direct 
contact. Xeisser destroyed it by heating to 60° C. 
for thirty minutes, but at this temperature for ten 
to twenty minutes its virulence for monkeys was 
retained. 

Prophylaxis demands no principles not generally 
known. 

Susceptibility to syphilis varies a great deal, not 
in the sense that some are immune, but in that a 
more virulent type of disease develops in some than 
in others. This is a condition, however, which 
is difficult to differentiate from variations in the 
virulence of the infecting agent. Syphilis is said 
to be particularly virulent when introduced into 
a race of people for the first time. 

The subject of immunity to syphilis is one of immunity. 
such proportions, the phenomena are so varied, 
and knowledge so inaccurate, that a thorough 
analysis can not be undertaken in this place. It 
is the customary belief that one attack confers 
permanent immunity to a second. To what ex- 
tent the acquired resistance to reinfection signifies 
a state of immunity is not satisfactorily settled. 
It seems well established that within a relatively 
short period following the appearance of a chancre 
a second primary lesion can not be acquired. It 
would be impossible to refer this resistance to ac- 
tual immunity in view of the fact that the indi- 
vidual is at the moment the subject of systemic 
infection. A second infection would be but a su- 



528 



INFECTION AND IMMUNITY. 



Serum 
Therapy. 



perimposed infection and may not be recogniz- 
able without the formation of a new chancre. The 
resistance which is continued into the tertiary 
stage, at a time when the individual usually has 
lost infectiousness for others, is equally obscure. 
If the present hope that Spirochetes pallida will 
be shown to be the cause of the disease is realized, 
and if experimental work with the monkey yields 
the results which it seems to promise, these and 
many other questions of fundamental importance 
may be elucidated. Among such questions are: 
the immunity of a mother who gives birth to a 
child infected by the father at the time of concep- 
tion (Collets law) ; the occasional occurrence of re- 
infection; the persistence of infectiousness and 
transmission of the disease into the third genera- 
tion, of which there are a number of reported ex- 
amples. 

Serum-therapy, or vaccination against syphilis, 
are possibilities of a future time. A truly anti- 
syphilitic serum has not yet been demonstrated. 
ISTeisser found the serum of syphilitics, from what- 
soever stage of the disease, without influence on 
the course of the infection. Also treatment with 
the normal serums of various insusceptible ani- 
mals has had no unqualified success. MetchnikofT 
and Roux observed a phenomenon which suggested 
to them the possibility of attenuating the virus 
so that it may be suitable for vaccination. A ma- 
cacus monkey reacted to inoculation by the produc- 
tion of a local lesion, the virus of which when 
transferred to the more susceptible chimpanzee 
likewise caused a local lesion, but no signs of gen- 
eralization appeared. The chimpanzee later showed 
himself resistant to the virus from man, and for 






YELLOW FEVER. 529 

this reason it was assumed that immunization had 
been accomplished. Neisser reasonably criticises 
this conclusion on the ground that the chimpanzee, 
having been inoculated with syphilis from the 
monkey, resisted inoculation from man, not be- 
cause he was immunized, but because he was syphi- 
lized, i. e., he was already infected with syphilis. 

III. YELLOAV FEVER. 

Yellow fever is peculiarly an American disease, occurrence. 
and it has reached other continents (e. g., Spain) 
only in accidental ways and for brief periods. It 
is possibly endemic in certain portions of West 
Africa (Sierra Leone), to which it was probably 
carried from, the Antilles (Scheube). Scheube 
regards the Antilles as the birthplace of yellow 
fever. Knowledge of it extends only to the middle 
of the seventeenth century, at which time it 
surely existed in the West Indies. The dis- 
ease has on several occasions been carried to 
Spain by vessels returning from Cuban ports. 
Until very recent times it was endemic in 
Cuba, especially Havana, and in Vera Cruz 
and other Spanish-American ports it has prevailed 
extensively. From such points extension frequent- 
ly takes place into adjacent tropical or subtropical 
regions, or even into temperate localities during 
the summer months. In the latter part of the 
eighteenth century Philadelphia suffered very se- 
verely. Baltimore was attacked similarly and Bos- 
ton to a less degree. Other northern ports, e. g., 
New York, have experienced attacks of limited 
duration, the disease, presumably, being intro- 
duced by means of infected ships. 

In addition to our southern coasts and that of 
Mexico, the Atlantic coast of South America has 



530 



INFECTION AND IMMUNITY. 



Bacillus 
Icteroides. 



The Mosquito 
Theory. 



been infected as far south as Buenos Ayres, and 
likewise the western coast of Mexico and Peru. In 
the eighteenth century the coast of Spain and 
Portugal suffered severely, but since that time 
only minor epidemics have occurred in these coun- 
tries. Epidemics frequently have appeared on 
ships after they had left infected ports. 

The Southern States were invaded repeatedly in 
the last decade of the eighteenth century, in 1803, 
1805, 1853, 1867, 1873, 1878, 1905, and in lesser 
degrees at other times, in all ninety-six times. The 
severest epidemics were those of 1853 and 1878. 

The many microbes which have been cited as the 
cause of yellow fever need not be described. The 
Bacillus icteroides of , Sanarelli, which had at- 
tained more prominence than any other, was shown 
by Sternberg, by Eeed and Carroll and by the more 
recent work on the mosquito theory, to bear no 
causal relationship to the disease. According to 
Eeed and Carroll it is identical with the hog-chol- 
era bacillus. 

The monumental work of Eeed, Carroll, Agra- 
monte and Lazear (1900), the last of whom lost 
his life from yellow fever, has made it possible 
to replace accurate knowledge of the epidemiology 
and prophylaxis of yellow fever and, to a certain 
extent, of its etiology, for many incorrect ideas 
which had prevailed up to that time. 

The conception that yellow fever is transferred 
from one person to another by mosquitoes was 
first advanced positively by Carlos Finlay, a 
Cuban physician, in 1881, although several Ameri- 
can physicians had long before noted the preva- 
lence of mosquitoes during yellow fever outbreaks 
(Eush, 1793; Weightman, 1839; Wood, 1853; 



YELL0 1 tY FEVER. 



531 



Barton, 1853). He reported the transmission of 
the disease, experimentally, by the bites of mos- 
quitoes which had fed on yellow fever patients, 
and stated that light attacks which followed the 
bites resulted in the establishment of immunity. 
The subsequent observations of Eeed and his co- 
workers indicate, however, that Finlay's technic 
was such that he could not possibly have produced 
experimental fever, and that the development of 
the disease in his subjects was purely a coincidence. 
The reason for this will appear below. 

Having satisfied themselves that Bacillus icte- 
roides is but an accidental organism in yellow 
fever, and that it is found under normal condi- 
tions as well, Eeed and his associates began work 
on the mosquito hypothesis of Finlay. The first 
positive result was obtained in the case of Dr. Car- 
roll. Carroll "was bitten at 2 p. m., Aug. 27, 1900, 
by Stegomyia fasciata. This particular mosquito 
had bitten a severe case of yellow fever on the 
second day of the disease, twelve days before; a 
mild case of yellow fever on the first day of the 
attack, six days preceding; a severe case of yellow 
fever on the second day of the attack, four days 
before; a mild case of yellow fever on the second 
day of attack, two days before inoculation." After 
an incubation period of three days, Carroll devel- 
oped typical and severe yellow fever, from which 
he recovered. A similar result in one other case 
was reported at this time, and later Camp Lazear, 
with mosquito-proof houses, was established for the 
continuation of the study. The experiments of 
Eeed and his co-workers, and confirmatory work by 
Guiteras and the French commission, can not be 
described in this place. We may feel sure, how- 



TheWorkef 
Reed, Carroll, 
Etc., with Stego- 
myia Fasciata. 



532 INFECTION AND IMMUNITY. 

important Facts ever, that with all the conditions of experimenta- 
Been Learned, tion under absolute control the following points 
have been determined with scientific certainty: 1. 
Yellow fever may be transferred from a patient to 
a non-immune by the bite of a mosquito — Stego- 
■ myia fas data — which has previously fed on the 
yellow fever patient. 2. In order that the mos- 
quito become* infected it is necessary for him to 
feed on yellow fever blood within the first few 
days (three days) of the fever. 3. The mosquito 
can not transfer yellow fever directly and imme- 
diately from the patient to a non-immune, but it 
is necessary for a period of not less than twelve 
days to elapse before he becomes infectious. When 
this time has been reached the insect continues in- 
fectious for at least fifty-seven days and probably 
throughout his life. 4. Yellow fever can not be 
transferred by "fomites." 5. The subcutaneous in- 
jection of yellow fever blood into a non-immune 
produces yellow fever, hence the infecting agent 
exists in the circulation. 6. The serum of a yel- 
low fever patient, after being diluted and filtered 
through a Berkefeld filter (Reed and Carroll) or 
Chamberland B porcelain filter (Rosenau, Parker, 
Francis and Beyer) is infectious, hence the in- 
fecting agent at some stage of its development is 
very minute, possibly ultramicroscopic. 7. "An 
attack of yellow fever produced by the bite of a 
mosquito confers immunity against the subsequent 
injection of the blood of an individual suffering 
from the non-experimental form of this disease" 
(Reed, Carroll and Agramonte). 8. The period of 
incubation usually is three days, but may vary 
within the limits of two to six days. 9. "A house 
may be said to be infected with yellow fever only 



and Steqomv ia 



YELLOW FEVER. 533 

■when there are present within its walls contami- 
nated mosquitoes capable of conveying the parasite 
of the disease." 10. "The spread of yellow fever 
can be most effectually controlled by measures 
directed to the destruction of mosquitoes and the 
protection of the sick against the bites of these 
insects." 11. No mosquito other than SUgomyia 
fasciata has been found capable of transmitting 
the disease, and analogies suggest the probability 
that no other insect is concerned. 

"These discoveries explain many facts in rela- Epidemiology 
tion to yellow fever which had been obscure hither- 
to. For example, yellow fever is a tropical and 
subtropical disease only because Stegomyia fas- 
ciata breeds in tropical and subtropical climates. 
The disease is found in low, moist localities rather 
than in the high and dry, because the mosquito in- 
habits the former and not the latter. Yellow 
fever dies out with the first severe frost or on the 
advent of cool weather because these conditions 
either kill the mosquito or cause him to hibernate. 
The advent of an initial case of yellow fever in a 
suitable region is followed by the appearance of the 
disease in epidemic form only after a period of two 
or three weeks, because the mosquito first becomes 
infectious in about two weeks after it has fed on 
yellow fever blood; this may correspond with a 
certain stage of development of the as yet unrecog- 
nized parasite. The observation often made that 
yellow fever, like malaria, is not contagious in the 
ordinary sense, in spite of its rapid extension, is 
readily understood, as is the irregular method in 
wihch the disease spreads. ' It is now clear why the 
disinfection of fomites has never been able to 
check the advance of an epidemic, and why the 



Distribution of 

Stegomyia. 



534 INFECTION AND IMMUNITY. 

ordinary quarantine measures which did not take 
the mosquito into consideration were not effective 
in keeping the disease out of a favorable port ; and 
by a favorable port is meant one which can harbor 
Stegomyia fasciata. These discoveries also ex- 
plain how yellow fever could be stamped out of 
Havana, Texas and New Orleans by prophylactic, 
hygienic and quarantine measures, which had as 
their objects the destruction of the mosquito and 
its breeding places and prevention of the infection 
of the mosquitoes by suitably screening the pa- 
tients. 

It is thus seen that the epidemic occurrence of 
yellow fever is strictly associated with the distribu- 
tion of Stegomyia fasciata. Howard, in Bulletin 
No. 46 of the Public Health Eeports, gives this 
distribution as known on Sept. 10, 1905, and pub- 
lishes a map showing the region which the insect 
may be expected to inhabit. 

Stegomyia fasciata has been found in the following 
localities in the United States (Howard) : 

Virginia: Virginia Beach, Norfolk, Lynchburg, Dan- 
ville, Richmond. Kentucky: Lexington, Middlesboro,. 
Louisville, Richmond. Illinois: Cairo. Tennessee: 
Nashville, Knoxville, Clarksville, Chattanooga, Memphis, 
Columbia, Decherd, Athens, Bristol. Arkansas: Hot 
Springs, Helena. Louisiana: Ruddock, New Orleans, 
Baton Rouge, Napoleonville, Covington, Hammond, 
Shreveport, Franklin, Morgan City, New Iberia, Patter- 
son. Mississippi: Pass Christian, Summit, Quarantine 
Station, Vicksburg, Clarksdale, Tutwiler, Belzoni, Holly 
Springs, Jackson, Wonona, West Point, Tupelo, Corinth, 
Agricultural College, Biloxi. Alabama: Mobile, Decatur, 
Auburn, Tuscumbia, Huntsville, Yazoo City. Georgia: 
Atlanta, Pelham, Augusta, Savannah, Brunswick. 
Florida: Barrancas, Key West. Texas: Galveston, 
Houston, Victoria, San Diego, Tyler, Laredo, Austin, 
San Antonio, Corsicana, Brownsville, Alice, Colorado, 
Dallas, Paris, Edna, Fort Bliss (El Paso), Fort Ring- 



YELL01Y FEVER. 535 

gold (Rio Grande-Ludlow). South Carolina: Charles- 
ton, Columbia, Fort Fremont, Sullivan's Island. Ari- 
zona : Nogales. Maryland: Baltimore (Carter) — breed- 
ing in fresh water on fruit wharf. North Carolina: Beau- 
fort, Winston, Raleigh, Greensboro, Charlotte, Salisbury. 
Indiana: Jeffersonville. Missoiwi: St. Louis. 

Eeed and Carroll found the larvae of stegomyia Breeding Places 
"(1) in rain-water barrels; (2) in tin cans that 
had been used for removing excreta and which 
still contained a small amount of fecal matter; 

(3) in sagging gutters containing rain water: 

(4) in cesspools; (5) in tin cans placed about 
table legs to prevent the inroads of red ants ; ( 6 ) 
in the collection of water at the base of the leaves 
of the agave americana; (7) in one end of a 
horse trough that was in daily use." These in- 
stances are cited to show the general character of 
the places in which the eggs and larvae of stegomyia 
may be found. The eggs are deposited during the 
night, in about seven days after the ingestion of 
blood, and "in pairs, in groups of three or more 
or singly/' to the number of forty-seven on the 
average (Reed and Carroll). The eggs are very 
resistant to drying and extreme cold ( — 17° C). 
With a favorable temperature they hatch in from 
three to seven days ; the larval stage lasts for seven 
days, the pupal two days, the total cycle being 
completed in about twelve days. As in the case of 
anopheles, only the female stegomyia sucks blood. 
The insect prefers the hours from 3 p. m. to 9 a. 
m. for feeding, but is most active from 4 p. m. 
to midnight. "In captivity the hungry impreg- 
nated female will bite at any hour of the day or 
night." In a state of freedom it will not bite a 
second time for from five to seven days. It ap- 
pears not to bite when the temperature is lower 



536 



INFECTION AND IMMUNITY. 



Importation 
by Ships. 



Time of than 62° F., another factor in the subsidence 
1 ,ng * of yellow fever with the advent of cool weather. 
For further details concerning the morphology, 
biology and habits of stegomyia consult Howard 
on "The Mosquito" ; Eeed and Carroll, "The Pre- 
vention of Yellow Fever," Medical Record, Oct. 
26, 1901; Parker, Beyer and Pothier, "Keport 
of Working Party No. 1" Yellow Fever Institute 
Bulletin No. 13, 1903, Washington. 

Yellow fever cases and stegomyia work together 
in the extension of the disease just as malarial 
cases and anopheles do in the extension .of ma- 
laria; for the principles involved the chapter on 
malaria may be consulted. Of particular interest 
is the importation of the disease by means of ships, 
since the invasion of the United States usually 
comes about in this way. It is frequently stated 
that ships lying one-half mile from shore are safe 
from yellow fever; G-rubbs, however, believes that 
stegomyia may reach vessels lying within fifteen 
miles of the shore if the wind is favorable. The 
insect readily boards a vessel lying in an infected 
port and may remain there at least during a sev- 
enteen days' voyage. It may also breed in suitable 
barrels or tanks of water on the ship. Under these 
conditions it is readily understood how a ship, 
leaving a harbor with a healthy crew, may be at- 
tacked by yellow fever a few days after leaving 
port; and how any quarantine measure at a new 
port which does not involve the destruction of the 
mosquitoes on the boat and the protection of the 
patients from the bites of mosquitoes is inadequate. 

As stated, the nature of the virus is unknown. 
Its filter ability was mentioned. A temperature 
of 55° C. for ten minutes renders innocuous 



Resistance 
of Virus. 



YELLOW FEVER. 



537 



the defibrinated blood of the infected ; according to 
the French Commission (Marchoux, Salimbeni 
and Simond) the virus is destroyed in five minutes 
at this temperature. The latter also found that 
defibrinated blood when sealed under vaselin re- 
tained its virulence for five, but not for eight days. 
The toxic substance appears to have a strong af- 
finity for the parenchymatous organs, particularly 
the liver and kidney. 

The essential principles of prophylaxis have Prophylaxis. 
been alluded to : 1, the destruction of breeding 
places for the mosquito as described in the section 
on malaria; 2, the isolation of patients, screened, 
to .exclude mosquitoes ; 3, the destruction of mos- 
quitoes found in infected houses or ships; 4, the 
individual factor of avoiding the bites of mos- 
quitoes, which involves the screening of houses, 
and individual care. One may go about more 
safely in the middle of the day than before 9 a. 
m. and after 3 p. m. For the disinfection of 
houses, i. e., for the destruction of mosquitoes, two 
pounds of tobacco or two pounds of pyrethrum 
powder per 1,000 cubic feet of space may be burned 
after the rooms are sealed. When smaller quan- 
tities are used the insects may be only stupified, 
and should be collected and burned (Rosenau, Par- 
ker, Beyer and Pothier). Sulphur dioxid is highly 
efficient, but formaldehyd is valueless as an in- 
secticide (Eosenau). 

The negro is less susceptible to yellow fever than Susceptibility. 
the white man and in him the mortality is lower. 
Among the natives the mortality is from 7 to 10 
per cent., among the whites from 20 to 80 per cent. 
(Scheube). The statement that Caucasians may 
become "acclimated" so that they are less suscep- 



Immunity and 
Serum Prop- 



538 INFECTION AND IMMUNITY. 

tible needs additional investigation. It seems im- 
possible that acclimatization could mean anything 
else than active immunization. Children and the 
aged are attacked less frequently than those be- 
tween the ages of ten and thirty. 

An attack of yellow fever, whether experimental 
erties. or natural, confers immunity of long or lasting du- 
ration. According to the French Commission, a 
certain degree of immunity could be conferred by 
the injection of infected serum which had been 
heated to 55° C. for five minutes, or of defibri- 
nated blood which had been kept under vaselin 
oil at room temperature for eight days. They also 
claimed that the serum of convalescents has pro- 
phylactic and curative properties to a certain de- 
gree. 

IV. TYPHUS FEVER. 

In addition to a streptobacillus obtained by 
Hlawa and the diplococci described by a number 
of investigators, a supposed protozoon, resembling 
pyroplasma, was found in six cases by Gotschlich. 
The etiologic role of none of these organisms can 
be accepted at the present time. 
occurrence Typhus is now a rare disease. It is* endemic on 
piousness. a small scale in London, Glasgow and Liverpool, 
and cases occur in the larger cities of Ireland. In 
epidemic form it attacks localities in which the 
hygienic conditions are bad. The contagion seems 
to fasten itself in such localities and does not ex- 
tend with rapidity to neighboring communities in 
which good hygiene and cleanliness prevail; it is 
particularly a disease of the poor, the filthy and 
the underfed. Healthy, clean and well-nour- 
ished persons who enter an infected district and 
come in contact with the patients are subject to 



TYPHUS. FEVER. 539 

attack. Typhus has always been considered a very 
contagious disease. It has been noted repeatedly, 
however, that when patients are removed to a hos- 
pital and kept under clean and hygienic conditions 
with plenty of fresh air that infection of attend- 
ants and physicians is relatively infrequent. From 
observation of 600 hospital cases Eobinson and 
Potts draw particular attention to this point and 
lay great stress on the importance of liberal ven- 
tilation in decreasing contagiousness. The method 
of transmission is not known. It has been sug- 
gested repeatedly that the disease may be spread 
by the bites of insects, perhaps fleas and bed-bugs. 
Gotschlich emphasizes the latter as possible car- 
riers, discrediting the significance of the flea. He 
notes that in Alexandria fleas are everywhere, 
whereas typhus is confined largely to the poorer 
and unclean localities. Transmission by means of 
clothing and other fomites is said to occur. Usual- 
ly the development of typhus in a hitherto unin- 
fected community is traceable to the importation 
of the disease; in some instances, however, the 
origin could not be learned. 

Prophylaxis demands the isolation and disinfec- 
tion usually practiced in combating contagious 
diseases, particular attention being paid to hygiene, 
cleanliness, the admission of fresh air to the sick 
room, and the destruction of vermin ( !). 

The serum of convalescents is said to be cura- 
tive in a moderate degree (Legrain). 

V. DENGUE FEVER. 

Dengue occurs in numerous countries which af- occurrence. 
ford a warm climate. It is endemic in Egypt, 
Arabia, Senegambia, Honduras, the Bermudas, 



540 



INFECTION AND IMMUNITY. 



and the Sandwich Islands. Important centers for 
the origin of epidemics are the lesser Antilles of 
the Western Hemisphere, the Eed Sea Coast, 
and Senegambia (de Brun, cited by Scheube). It 
occurs in our southern states and in Mexico. It 
may be introduced into new regions by means of 
infected ships. 
Organisms. The specific agent is unknown. The "plasmeba" 
described by Eberle (1904) and his hypothesis that 
Culex fatigans may transmit the disease await con- 
firmation. The same may be said of an influenza- 
like organism seen by Carpenter and Sutton 
(1905) in stained preparations from the throat. 

"Dengue fever is an acute infectious disease, 
distinguished by the appearance of an initial and 
terminal polymorphous eruption and accompanied 
by severe articular and muscular pains." Corre- 
sponding with the two eruptions, there are charac- 
teristically two periods of temperature separated 
by a short period of apyrexia. The intense muscu- 
lar pains and asthenia resemble those of influenza, 
the respiratory affections of the latter being absent, 
however. The incubation period varies from a few 
hours to four or five days, usually one or two, and 
the entire duration from six to seven days. 
Transmission. Dengue fever extends epidemically with all the 
rapidity which characterizes influenza. "In some 
respects the spread of the disease suggests some 
peculiarity in the method of propagation differing 
from that of the well-known diseases, influenza, 
scarlet fever, measles, etc. It appeared to spread 
particularly to contiguous houses, whole streets 
being attacked seriatim."* Dengue prevails espe- 



* "Ileport on the Dengue Epidemic in Brisbane in 1005." 
Committee of Queensland Branch of the British Medical 
Association. Journal of Tropical Medicine. Dec. 15. 1005. 



DENGUE FEVER. 541 

dally during the hot months. "A great fall of 
temperature and the appearance of absolutely cold 
weather always puts an end to the epidemics" 
(Hirsch, cited by Scheube). 

The disease extends so rapidly, and the incuba- 
tion period is so short, that general measures of 
prophylaxis would seem to be of no avail. 

Susceptibility is general, even in infancy and 
old age. The disease has a very low mortality; 
it is more severe in very early and very late life. 
Relapses are not infrequent, and one attack does 
not confer immunity. Second attacks may occur 
during the same year. Leucopenia is present from 
the first (Carpenter and Sutton). 

VI. ACUTE ARTICULAR RHEUMATISM. 

(See pp. 359, 360.) 

VII. SMALLPOX AXD VACCINIA. 

Vaccinia and smallpox may be considered to- Relation of 
gether, having in mind the likelihood or, indeed, smaWpoV. 
the certainty, that they have a common etiology. 
This view seems the only possible one, in spite of 
our uncertainty as to the exact nature of the cause. 
To hold a different view would be to acknowledge 
that immunization with one kind of microbe may 
confer immunity of the strongest and most spe- 
cific character against another, a condition for 
which we could find no parallel. 

More satisfactory knowledge, however, comes inoculation of 
from actual conversion of smallpox virus into vac- s™HpoxT ith 
cine virus by passing the former through cows. 
Abbot quotes W. J. Simpson as follows : "In No- 
vember, 1885, with smallpox lymph from an un- 
vaccinated patient, 1 inoculated a cow with fifth- 
day lymph and a ewe with eight-day lymph from 



542 



INFECTION AND IMMUNITY. 



the same patient. Both presented vesicles on the 
seventh day, the lymph of which I sent to London 
to be used by Dr. Cory, the director of the Animal 
Vaccine Institute of London. This calf lymph, 
which Dr. Cory passed through a second calf before 
using it on children, was the starting point of a 
new vaccine at the institute. Between Nov. 21, 
1885, and May 6, 1886, 1,247 children had been 
vaccinated with this lymph and gave 98.4 per 
cent, insertions of success." 

Concerning the changes which smallpox virus 
undergoes in the cow, as a result of which it loses 
permanently the power of causing smallpox in 
man, we have no knowledge, aside from the hy- 
pothesis of Councilman and others mentioned below. 

Etiology. "We may pass over the various bacilli and cocci 
which have been described as causing vaccinia and 
smallpox with the- remark that none of them are 
of primary significance, but that they have been 
either accidental contaminations or the causes of 
secondary infections during the course of the dis- 
ease. 

Theories. There are two chief theories as to the cause of 
smallpox (and vaccinia) to-day. One, that the virus 
is an ultra-microscopic and uncultivatable organ- 
ism ; and a second, that it is represented by certain 
protozoon-like bodies seen in the specific lesions 
(vesicles, pustules) of both vaccinia and smallpox. 
Concerning the first theory we know nothing be- 
yond the observation of Parke that the virus of both 
vaccinia and variola did not pass through Berke- 
feld and Chamberland filters under the conditions 
of his experiments. Of the second theory a brief 
review may be given. 

Protozoon-like bodies have been seen by many 



SMALLPOX AXD VACCINIA. 543 

observers and were first brought into causal rela- Cytoryctes 
tion with smallpox by Van der Loeff and by L. Protozoom?) 
Pfieffer (1887). Gnarnieri (1892), however, gave 
the subject its present impetus by a careful study 
of these forms as seen in vaccinia and gave to the 
hypothetical organism the name of Cytoryctes vac- 
cinia, s. variolce. The bodies were found within 
the deep epithelial cells in the pustules of vaccinia 
and smallpox and in the lesions produced on the 
cornea of the rabbit by inoculation with the viruses 
of vaccinia and smallpox. They lie within clear 
spaces in the protoplasm of the cells, vary in size 
from that of a micrococcus to that of an epithelial 
nucleus and multiply, it was supposed, by binary 
division. When mounted in hanging-drops of the 
vesicular fluid they showed ameboid movements. 
Confirmatory work came from others, and partic- 
ularly Wasielewski, who concluded that the "vac- 
cine bodies" are perfectly characteristic, that they 
are never found in normal or other pathological 
conditions of the skin, that they can not originate 
from leucocytes or epithelial cells, and hence can 
not be accidental "cell inclusions." Filtered virus 
produced no lesions in the cornea of the rabbit. 

Eecently Councilman, Magrath and Brincker- work of 
hoff have studied this supposed organism in great and others. 
detail and find, in addition to the forms in the cy- 
toplasm (cytoplasmic parasites), still others within 
the nucleus of the epithelial cells of the vesicles 
and pustules. They express the belief that the or- 
ganism first gains entrance in the cytoplasm of the 
cells, and after a period of "multiplicative prolif- 
eration," the products of the latter process pene- 
trate the nuclei of the epithelial cells and there 
undergo another type of proliferation. Calkins, 



544 



INFECTION AND IMMUNITY. 



Life History 
of Cytoryctes. 



the zoologist, after studying the material, shares 
their -views and has constructed a life cycle of the 
parasite from the various forms which he found in 
fixed and stained preparations. 

The smallest recognizable forms in the cytoplasm 
measure about 0.7 of a micron and lie in a vacuole in 
the cytoplasm near the nucleus. Calkins interprets 
these as "gemmules" and as products of the prolifera- 
tion of the parasite at the primary point of infection 
( lungs ( ? ) ) . Somewhat larger forms ( 3 microns ) con- 
taining a vacuole with a central point staining with 
methylene blue, represent "gemmules" which have grown 
and have become somewhat differentiated. The periphery 
Cytoplasmic of the organism becomes differentiated also by the for- 
Stages. m ation of minute dots which may eventually be stained 
by a special method. During this stage the organism 
"often is spherical, but may be fusiform, pyriform or 
ameboid, while pseudopodia are frequently caught in 
various degrees of extension." No definite nucleus is 
discernible, but material corresponding to nuclear sub- 
stance is distributed somewhat generally through the 
parasitic cell. Certain granules are distributed through- 
out the body of the organism, and these granules eventu- 
ally give rise to the "gemmules" or young parasites 
which become free by the disintegration of the mother 
cell. 

Howard and Perkins find, in addition to the cyto- 
plasmic stage of Councilman and his co-workers, a sec- 
ond cytoplasmic stage, the products of which penetrate 
the nucleus to institute the intranuclear stages. Cal- 
kins speaks of the fate of the gemmules as follows: 
"The germs formed by the multiplicative reproduction 
of the cytoplasmic ameboid form of the parasite may 
develop into new cytoplasmic organisms or ultimately 
may become germ cells within the nucleus of the epithe- 
lial cell. In the latter case they develop into struc- 
tures which I regard as gametocytes. The resulting 
zygote (formed by conjugation of the gametes) is the 
ameboid pansporoblast mother organism." 

The conclusion that conjugation takes place is based 
on certain analogies with other micro-organisms, rather 
than on observation of the phenomenon. This intra- 



Nuclear 
Stages. 






SMALLPOX AND VACCINIA. 545 

nuclear mother organism, the product of conjugation, 
finally grows to a size of 10 to 12 microns and forms 
within it from eight to twenty "primary sporoblasts." 
The young sporoblasts are eventually liberated from the 
mother cell and are at first solid and homogeneous, like 
the gemmules, but later when they have reached a size of 
iy 2 to 2 microns small vacuoles appear in the peripheral 
ring of substance and in each vacuole a young spore is 
formed. The formation of these spores terminates the 
"primary nuclear phase" of the organism. These spores, 
still within the nucleus of the epithelial cell, become, 
in their turn, sporoblasts, and the formation of a large 
number of secondary spores within them constitutes the 
secondary nuclear phase of the parasite. In the mean- 
time the nucleus of the epithelial cell has degenerated, 
and the secondary sporoblast with its contained spores 
escapes first into the cytoplasm and eventually into the 
pericellular space. In accordance with this conception 
the intranuclear process is well calculated to give rise 
to a massive number of young parasites within the body. 
Councilman, Magrath and Brinckerhoff state that after 
the tenth day of the disease the parasites become more 
and more difficult of recognition by microscopic methods. 
However, Brinckerhoff found that even the desiccated 
crusts of pustules and vesicles produce typical lesions 
on the cornea of the rabbit. These forms have never 
been recognized positively in the blood of patients, and 
Magrath and Brinckerhoff were not able to produce le- 
sions in the rabbit's cornea by inoculation of variolous 
blood. The general distribution of the lesions in the 
skin and the occurrence of fetal smallpox gives us abun- 
dant reason for believing that the blood stream is in- 
vaded by the parasites. 

It was stated above that bodies of the general nature Cytoryctes in 
of those described are found in vaccinia as well as in Vacc ' n ' a « 
smallpox, and this occurrence is some added reason for 
believing that Cytoryctes variolar, s. vacciniw, is the ' 
cause of these processes. It is a most interesting and 
important observation by the American authors cited 
that the intranuclear stage of the parasite does not 
occur in vaccinia (Tyzzer), and we are led to believe 
that this is an important differential point between 



546 



INFECTION AND IMMUNITY 



Infection 
Atrium. 



Dissemination. 



vaccinia and smallpox. Assuming that the bodies in 
question cause the disease, the thought is pertinent that 
the difference in virulence between vaccinia and variola 
inoculata may depend on the failure of the intranuclear 
cycle to appear in vaccinia. 

The work of Gkiarnieri, and particularly that of 
Councilman, Magrath and Brinckerhoff, is most 
suggestive, and ardent supporters of their views 
have appeared with corroborative work (e. g., How- 
ard). At the same time many skilled observers 
discredit entirely the parasitic nature of the bodies 
described, interpreting them rather as products 
of degeneration of the epithelial cells and nuclei 
or as inclusions of other tissue cells (e. g., leuco- 
cytes, Borrel) or fragments of other nuclei. Ewing 
expresses similar views. The state of the question 
is such that further study is urgently called for. 

We have no positive knowledge as to infection 
atrium in smallpox, although the existence of a 
"contagious zone" of atmosphere about the patients 
is good ground for the belief that invasion takes 
place through the respiratory passages. The disease 
which follows introduction of the virus into the 
skin is spoken of as variola inoculata, and is much 
less severe than smallpox. We are also ignorant to 
a large degree of the means of excretion or dissem- 
mination of the virus. Osier states that the virus 
"exists in the secretions and excretions and in the 
exhalations from the lungs and skin." The dried 
epithelial cells which are continuously thrown off 
are no doubt a most important means of dissemina- 
tion. Infection may be transmitted by means of 
clothing or other materials which have been in con- 
tact with patients, and the disease may be carried 
to others from the sickroom by a healthy person. 



SMALLPOX AXD VACCINIA. 547 

Epidemiologic experience teaches that the virus is 
one of great resistance and tenacity. 

The incubation period in variola falls within the Cyclic Nature 
extremes of eight to twenty days, most commonly 
from nine to fifteen days. The stage of invasion, 
or the primary fever, terminates the incubation 
period, and during this time the initial rash ap- 
pears, accompanied by moderate hyperleucocytosis. 
On the third to the fourth days the remission sets 
in, the number of leucocytes in the blood decreases 
to normal or below normal, and cutaneous lesions 
make their appearance, and in the course of forty- 
eight hours show a vesicular nature. When the 
umbilicated vesicles are changed into pustules the 
temperature again rises (secondary fever) and hy- 
perleucocytosis again develops. This much only 
of the clinical picture is mentioned to emphasize 
the cyclic nature of the phenomena ; one may well 
suspect that the organism causing such a disease 
undergoes particular phases of development which 
in some way are related to the well-known clinical 
cycle. 

Epidemics are sometimes of so mild a charac- vfruJence* '" 
ter that the patients are not bed-ridden and may 
be found in the pursuit of their occupations in 
spite of well-marked eruptions. Such occurrences 
can be referred only to a virus of low pathogeni- 
city. Even mild epidemics, however, may be ac- 
companied by severe and fatal cases. Cases of am- 
bulatory smallpox are most important factors in 
spreading the disease. 

We have nothing more than presumptive knowl- Jj^JjJjfV*" 
edge concerning the distribution of the virus in the Body. 
the body aside from its occurrence in the skin and 
mucous membranes. We may feel certain, how- 



548 INFECTION AND IMMUNITY. 

ever, that the infection is systemic. The lesions 
of the skin are of such a nature that they are 
generally regarded as of embolic character, which 
presupposes blood infection; and transmission of 
the disease through the placenta is decisive proof 
of a general distribution of the virus at some stage 
of the process. The failure to cause vaccinia in 
the cornea of the rabbit by inoculating the blood 
of patients (cited above) may indicate that the 
virus is present in the blood in small quantity or 
that circulating organisms are eventually de- 
stroyed. The intoxication of smallpox is mani- 
festly general. 
Secondary In few diseases does secondary infection play so 
important a role as in smallpox. When the cu- 
taneous lesions have become pustular they usually 
contain pyogenic cocci, although they may be ab- 
sent. It is somewhat strange that streptococci are 
more often encountered than staphylococci, in 
view of the normal presence of the latter in the 
epidermis. Fatal cases are almost without excep- 
tion accompanied by general streptococcus infec- 
tions, and Councilman believes these organisms 
are more important as a cause of death than the 
specific virus. 
Prophylaxis. Successful prophylaxis involves universal vac- 
cination, in addition to special measures which are 
demanded in the presence of the disease: isola- 
tion of the sick until desquamation is complete, 
antiseptic baths, and disinfection and fumigation 
as currently practiced. 
Discovery of Interesting matters of history are the facts that 
vaccination. p ro ^ ec ^-[ ve inoculation against smallpox was prac- 
ticed in fairly ancient times by rather primitive 
races, and that Lady Mary Wortley Montague 



SMALLPOX AND VACCINIA. 549 

introduced this method into Europe in 1718. 
This was not the vaccination in vogue to-day, 
however, but rather the inoculation of virulent 
virus from the pustules of the diseased into the 
healthy. As mentioned in one of the earlier chap- 
ters, this procedure commonly produced a mild 
type of disease (variola inoculata) which ren- 
dered the individual immune to virulent small- 
pox. 

Everyone knows that the vaccination of to-day, Jenner. 
i. e., the substitution of the virus of cowpox for 
that of smallpox, was the discovery of Jenner 
(1798), and we need offer no comments concern- 
ing its efficacy nor repeat the well-earned epithets 
which have been applied to the rare species of dis- 
believers. Nothing is more certain than that 
smallpox has ceased to be a world pest only be- 
cause of the continued Jennerization of the race. 

The essential points established by Jenner are 
the following: 1. That the vaccine disease 
casually communicated to man has the power of 
rendering him insusceptible to smallpox. 2. That 
the specific cowpox alone, and not other eruptions 
affecting the cow which might be confounded with 
it, has this protective power. 3. That the cow- 
pox may be communicated at will from the cow to 
man, by the hand of the surgeon, whenever the 
requisite opportunity exists. 4. That the cowpox, 
once engrafted on the human subject, may be con- 
tinued from individual to individual by successive 
transmissions, conferring on each the same im- 
munity against smallpox as was produced in the 
one first infected directlv from the cow (cited 
from S. W. Abbott). 

For at least half a century following Jenner's 



550 



INFECTION AND IMMUNITY. 



Cowpox. 



Humanized discovery humanized lymph was used for vacci- 
nation, new patients being inoculated by means 
of points prepared from vesicles of previous cases, 
or with the fresh lymph from such cases. The not 
infrequent transmission of syphilis by this means 
was the source of many calamities. Following the 
precedent of Warlemont in 1868, the lymph of 
cowpox is now the universal source of vaccine. 

Cowpox probably occurs to a greater or less 
degree in all countries, especially in the spring and 
summer, attacks the udder and teats almost ex- 
clusively, and is accompanied by very mild con- 
stitutional symptoms. The incubation period is 
from three to eight days. There is first local 
heat, swelling and tenderness, followed by the for- 
mation of papules, which in three or four days 
after their appearance are transformed into vesi- 
cles. The disease reaches its maximum develop- 
ment at the tenth or eleventh day, the umbilicated 
vesicles going through the usual course to crust 
formation. 

Calves and heifers from the age of two months 
to two years are best suited for vaccination in the 
production of lymph for commercial purposes. 
The region of the flank or the whole ventral sur- 
face of the body may be inoculated, and in the lat- 
ter instance as many as a hundred or more inser- 
tions may be made. The skin is first shaved, 
cleansed with antiseptics, and the lymph from an- 
other calf is introduced by means of a syringe or 
by scarification. In some institutions long, very 
superficial parallel incisions are made and the 
virus rubbed in with a spatula. Within five days 
to a week the vesicles are in such condition that 
the lymph may be collected, the contents either 



Preparation 
of Vaccine. 



SMALLPOX AXD VACCINIA. 



being squeezed out with suitably formed forceps 
or scooped out with a sharp spoon. Depending on 
the area vaccinated, the lymph collected from a 
single calf may be sufficient for from 2,000 to 
15,000 vaccinations in man. In view of the im- 
munity which is conferred calves can be used but 
once for the production of vaccine virus. 

All other methods of preserving lymph have 
been largely abandoned for the process of 
glycerinization, the glycerin being very inti- 
mately mixed with the virus by mechanical 
means and allowed to remain in this state in 
a cool place for from six to eight weeks before 
the product is put on the market. Dried vaccine 
on ivory points is still used to some extent, the 
points being coated directly from the vesicles. 
Dried vaccine retains its power for from two to 
four months or longer when kept in a cool, dark, 
dr} r place. Glycerinated lymph has many advan- 
tages, the most important of which relates to the 
bactericidal action of the glycerin by which the 
lymph is freed from the pathogenic bacteria (e. g., 
staphylococci) which in former times caused ser- 
ious complications in vaccination. The glycerin 
is supposed to destroy such organisms to a large 
degree without, however, injuring the vaccine 
virus itself. It is also stated that glycerinated 
lymph is much more durable than the dried ; that 
its potency may be retained for eight months or 
longer under suitable conditions. Eosenau has 
recently called attention to the fact that the bac- 
tericidal power of glycerin lias been overestimated, 
and that while it kills pyogenic cocci within two 
weeks when at the body temperature, such organ- 
isms may live for months in glycerin when in the 



Glycerinization 



Effect en Con- 
taminating 
Bacteria. 



552 INFECTION AND IMMUNITY. 

ice chest; and, of course, onr glycerinated virus 
is kept in the ice chest. Tetanus spores live for 
months in glycerin and glycerin has practically 
no neutralizing action on tetanus toxin. Glycerin 
does have the power, however, of attenuating the 
tetanus spores, and its slow bactericidal action is 
well established. As stated above, the vaccine 
should be glycerinized for some weeks before it is 
put on the market. Glycerin has the added ad- 
vantage for the manufacturer of enabling him to 
dilute his lymph moderately (50 to 60 per cent.) 
without impairing the virus. 

Of much more importance for the safety of 
virus than glycerinization are proper hygiene and 
cleanliness during the whole process of prepara- 
tion. The powers recently conferred on the Sur- 
geon-General by an act of Congress have resulted 
in a great improvement in the purity of the vac- 
cine now on the market.* 

While it can not be expected that vaccine will 
be entirely free from bacteria, it is possible to re- 
duce their number to a low minimum and to elim- 
inate pathogenic forms, particularly pathogenic 
cocci, tetanus and tubercle bacilli. 
vaccination The technic of vaccination is so well known 
that no description is needed. It need only be 
stated that in scarifying it is undesirable to 
cause hemorrhage and that the operation is a sur- 
gical procedure, demanding surgical cleanliness 
and surgical care of the wound. As a rule vac- 
cination in man protects against smallpox for a 
period of six to ten years, after which revaccina- 
tion is necessary for continued protection. It 

* John F. Anderson "Federal Control of Vaccine Virus," 
Jour, of the Amer. Med. Assn.. June 10. 1905. 



SMALLPOX AXLJ TACCIXIA. 553 

should not be concluded from the negative out- 
come of a single vaccination that the individual is 
immune to vaccination and hence immune to 
smallpox, but rather, repeated attempts should be 
made with virus known to be fresh. It is quite 
possible that certain individuals are immune to 
vaccinia, as often stated, but they are very rare, 
and the condition should not be recognized nastily. 
Among 38,000 vaccinations Dr. Cory encountered 
but one in which a "take" could not be gotten on 
second trial (Abbott). 

The ideal condition is that all children should when to 

Vaccinate. 

be vaccinated at an early age by requirement of 
law as in certain European countries, where it is 
demanded within the first few months or the first 
year or two of life. Some countries require re- 
vaccination before the children are admitted to 
school and recommend repetitions at suitable in- 
tervals. 

We have no national law on the subject and the 
state laws differ. In many states children must 
be vaccinated before they are admitted to the pub- 
lic schools, the responsibility sometimes falling 
on the school and sometimes on the city or town 
authorities. A number of states have no laws on 
the subject, although vaccination is for the most 
part assured through the requirements of the 
State Boards of Health and the local authorities. 

When there is danger of an epidemic, and in 
known cases of exposure, vaccination should be 
practiced thoroughly. Inasmuch as the incuba- 
tion period of vaccinia is about three days less 
than that of smallpox, successful vaccination pro- 
tects within a limited period following exposure. 
Immediate vaccination is demanded in case of 



554 



INFECTION AND IMMUNITY. 



Immunity and 
Susceptibility. 



exposure. Healthy infants may be vaccinated 
within the first six weeks or two months of life 
and at any earlier period in case of exposure. 

An attack of smallpox confers prolonged and, 
with few exceptions, lasting immunity. Second 
and even third attacks have been described. It is 
known that those who have had smallpox may be- 
come susceptible to vaccination after a period of 
time. Susceptibility varies a good deal with age. 
During the ages of from two to fourteen years 
the disease is less common than between fifteen 
and forty, and after this period it again decreases 
in frequency. Undoubted instances of natural 
immunity to smallpox occur, but they are very 
rare. 
Leucocytes. Smallpox is accompanied by a leucocytosis 
which is peculiar because of the large number of 
mononuclears. There is a slight rise in the 
number of leucocytes during the first febrile on- 
set, a fall to almost normal during the remission, 
followed by a second rise, which may be as high 
as 16,000 to 20,000. Fatal cases show a terminal 
hypoleucocytosis (Magrath, Brinckerhoff and Ban- 
croft). Large numbers of lymphocytes are also 
found in the pustules (Eoger). Nothing of a sat- 
isfactory nature is known concerning the relation- 
ship of the leucocytes to recovery and immunity. 

There is no serum therapy for smallpox. The 
interesting observation has been made, however, 
that the serum of convalescents or of vaccinated 
man or animal will, when mixed with vaccine 
virus, prevent its action. 

Horsepox is identical with cowpox. Sheeppox 
(clavelge) is an independent disease. The virus of cow- 
pox produces a local lesion in the sheep, but does not 



Serum. 



CHICKEXPOX. ooo 

cause immunity to sheeppox. The virus of sheeppox, on 
the other hand, has no effect on horses and cattle 
(Xocard and Leclainche). The virus of sheeppox is 
filterable (Borrel). 

VIII. CHICKENTOX ( VARICELLA ) . 

Although the skin manifestations of varicella 
often resemble those of smallpox to such an 
extent that differentiation is difficult., the two 
diseases are distinct. Nothing indicates this more 
clearly than the fact that one who has recovered 
from varicella is susceptible to vaccination, and it 
is known further that an attack of chickenpox 
does not protect against smallpox. 

The etiology is unknown, and no organism 
which has been described can be considered the 
probable cause. 

Varicella occurs epidemically and sporadically. 
The virus probably exists in the lesions of the 
skin and in the scales, and the latter may be the 
chief source of contagion. There is no definite 
knowledge concerning the resistance of the virus, 
nor its distribution; the conclusion is justified, 
however, that it exists in the circulation at least 
in an early stage of the disease. The infection 
atrium likewise is a matter of conjecture, but 
probably is to be found in the lungs or upper 
respiratory tract. 

The patients should be isolated and school chil- 
dren should not be allowed to return to school 
until desquamation is complete. Disinfection 
should be practiced. 

Susceptibility and virulence would seem to vary, 
since the severity of the cutaneous lesions is not 
constant. In delicate and tuberculous children, 
tbe lesions may become gangrenous. Hemorrhagic 



556 INFECTION AND IMMUNITY. 

varicella is observed occasionally. Such compli- 
cations as nephritis and otitis media occur. 

Varicella is a disease of childhood, although it 
may occur in adults. Infants are attacked less 
frequently. Second or even third attacks occur, 
although they are rare. 

There is no serum therapy. 

IX. SCARLET FEVER. 

The role which the streptococcus plays in scarlet 
fever was considered on page 361. 

The bodies" recently observed by Mallory may 
be referred to briefly. 
TheProto- In 1903 Mallory described certain protozoon- 
z ° Mai lory, like bodies found in the skin of four cases. They 
could be divided into two groups, one of which 
consisted of "round, oval, elongated, lobulated 
bodies" from 2 to 7 microns in diameter ; the indi- 
viduals of the second group "contain a central 
round body, around which are grouped, on optical 
section, from 10 to 18 narrow segments, which, in 
some cases, are united, but in others are sharply 
separated laterally from each other." They occur 
within and between the epithelial cells and in the 
superficial part of the corium. He gives the name 
of Cyclaster scarlatinalis to these bodies, and, al- 
though expressing the belief that they are protozoa 
and have a causal relation to scarlet fever, does not 
claim to have proved such a relation. 

Duval corroborated the discovery of Mallory, 
and demonstrated the bodies in five out of eighteen 
cases in blisters which were produced artificially 
during the height of the eruption. Field found 
them not only in the skin of scarlet fever, but also 
in that of measles and concludes that many of 



SCARLET FEVER. 557 

them at least represent artifacts or degeneration 
forms of tissue cells. More extensive observations 
seem to be necessary to establish the nature of 
these supposed parasites. 

Other micro-organisms which have been de- 
scribed as the cause of scarlet fever, including the 
Diplococcus scarlatina of Class, we may pass over 
with the remark that the claims concerning them 
have not been upheld. 

The contagiousness of scarlet fever is extreme, andean"-" 688 
and the virus undoubtedly is thrown into the sur- mission. 
rounding air from the skin of the patient. It is 
highly probable that the virus also reaches the sur- 
rounding air from the respiratory passages by 
means of "drop infection," since transmission may 
occur before the skin shows involvement. Patients 
continue to be infectious for from 4 to 6 weeks or 
longer after the appearance of the eruption. The 
disease may be transmitted by an intermediate 
healthy person, or by contaminated clothing or 
furnishings. The origin of epidemics from milk 
which has in some way been contaminated seems 
to have been proved in a number of instances. 

Of great importance for the persistence of an 
epidemic is the resistance of the virus, which re- 
mains viable and virulent for months and possibly 
for years, when under suitable conditions. 

Prophylaxis demands isolation of the patients Prophylaxis. 
until desquamation is complete; the use of anti- 
septic baths or ointments, or vigorous scrubbing 
with soap as desquamation proceeds; antiseptic 
treatment of the mouth cavity; disinfection of all 
utensils, linen, etc., with which the patient has 
been in contact ; avoidance of stirring up the dust 
in the room, which demands moist rather than dry 



558 



INFECTION AND IMMUNITY. 



Susceptibility 
and Immunity. 



cleansing; the disinfection of the sputum and 
other discharges of the patient; an abundance of 
fresh air and sunshine in the sick room; the final 
disinfection of the room. Physicians and nurses, 
when in the presence of the patient, should wear 
long gowns, which can be discarded on leaving, 
and other well-known precautions should be ob- 
served to avoid spreading of the disease. 

Scarlet fever is particularly a disease of child- 
hood, "a large proportion of cases occurring before 
the tenth year" (Osier). Adults are attacked not 
infrequently. Infants are less susceptible than 
older children. Many examples of family immun- 
ity, which probably is relative, are encountered, 
and likewise instances in which there is a family 
susceptibility. In a given family examples of in- 
dividual immunity and susceptibility are fre- 
quently met with. One attack usually confers im- 
munity against a second, but not invariably. 
Leucocytes. Scarlatina is characterized by a leucocytosis, 
the degree of which bears some relation to the 
severity of the infection. In mild cases the aver- 
age is from 10,000 to 18,850 (Bowie), in moder- 
ately severe cases from 20,000 to 40,000, or even as 
•high as 78,000 (Klotz) ; in malignant uncompli- 
cated cases there is a tendency to a low leucocyto- 
sis (Klotz). How much of this leucocytosis de- 
pends on co-existing streptococcus infection re- 
mains uncertain. 

Treatment with antistreptococcus serum is the 
only serotherapeutic measure which has been ad- 
vocated in relation to scarlet fever. This is done 
either on the assumption that the disease is of 
streptococcus etiology, satisfactory proof of which 
has not yet been obtained, or with the hope that 



Serum 
Therapy. 



MEASLES. 559 

the serum will influence favorably secondary in- 
fections with the streptococcus. The serums of 
Aronson, Moser and of Menzer have been tried 
more than others. Moser is probably more enthu- 
siastic than others, and he claims a reduction in 
the mortality from an average of 13.08 per cent. 
to 8.9 per cent, in 400 cases. Others have observed 
a favorable influence in some cases, but the re- 
sults are not uniform. The development of sec- 
ondary streptococcus infections can not be pre- 
vented by the use of the serums, although it is 
stated that their severity may be moderated. 

Of theoretical interest is the report by Weiss- 
becker and by v. Leyden that the serum of con- 
valescents causes a reduction of the temperature 
and a shortening of the course of the disease. 

The results published up to the present time 
indicate that we have not as yet an efficient serum 
for scarlet fever (see also p. 367). 

x. MEASLES. 

Bacilli which have been recognized in the con- Micro- 



organisms. 



junctiva, sputum and nasal passages in cases of 
measles have, for the most part, resembled either 
the diphtheria or the influenza bacillus. Pseudo- 
diphtheria bacilli are normal residents in the eye, 
and influenza-like bacilli are found in the sputum 
in various conditions; hence, there is insufficient 
reason to associate such organisms with the etiol- 
ogy of measles. The micrococci found by Lasage 
(1900) have not received recognition as the cause 
of the disease. 

Measles is highly contagious, even during the Distribution of 
prodromal stage. The contagion doubtless is ex- theV,ru8, 
creted from the lungs as well as the skin, and, in 



560 



INFECTION AND IMMUNITY 



Effect on 
Resistance. 



Prophylaxis. 



view of the early bronchial symptoms, the virus 
probably gains entrance through the hmgs. Suc- 
cessful inoculation into man with blood taken 
from the involved skin shows that the virus exists 
in the circulation of the skin. Hektoen doubts 
the decisiveness of a number of these experiments 
since they were carried out in the presence of 
epidemics and natural infection could not be ex- 
cluded; at the same time he does not question the 
results of Mayr (1852) . In two experiments on man 
Hektoen determined the presence of the virus in the 
blood. "The results of these two experiments per- 
mit the conclusion that the virus of measles is 
present in the blood of patients with typical 
measles some time at least during the first 30 
hours of the eruption; furthermore, that the virus 
retains its virulence for at least 24 hours when 
such blood is inoculated into ascites-broth and kept 
at 37° C. This demonstration shows that it is 
not difficult to obtain the virus of measles unmixed 
with other microbes and in such form that it may 
be studied by various methods." The virus is 
much less resistant than that of scarlet fever. The 
varying grades of severity of different epidemics 
show that it is subject to alteration in its virulence. 

Although measles is considered somewhat harm- 
less on the whole, dangerous complications, such 
as broncho-pneumonia and otitis media, are suffi- 
ciently frequent. The development of tuberculosis 
following measles, an event which is not uncom- 
mon, shows that measles may greatly decrease gen- 
eral resistance. 

The prophylaxis of measles is not different from 
that of other exanthemata. The isolation should 
continue for four weeks after the appearance of the 



MEASLES. 



561 



exanthem (Gotschlich). The sickroom should be 
disinfected eventually. The view not uncommonly 
encountered that measles is a good thing for a 
child to have and be over with is in no way justifi- 
able. The development of serious complications 
can in no case be foreseen, and fatalities may occur 
even in mild epidemics. 

Very young children, the rachitic and tubercu- susceptibility 
lous, and those in a poor state of nutrition should rence ecur " 
be guarded against exposure, for in them measles 
is often malignant. Infants are less susceptible 
than older children. Measles occurs in adults more 
frequently than scarlet fever. Kecurrences, on the 
whole, are frequent, as many as four attacks hav- 
ing been noted in an individual. Hence, the im- 
munity caused by infection is not uniformly of a 
permanent character. 

It is very probable that the inhabitants of a Racial 
country in which measles is endemic gradually 
become immunized, with the result that the disease 
prevails in a mild form. On the contrary, regions 
in which measles has hitherto been unknown, or 
has been absent for many decades, are susceptible 
to visitations of great malignancy. Such epi- 
demics have occurred in the Faroe Islands and in 
Iceland, with a mortality exceeded by few epi- 
demic diseases. 

A moderate leucocytosis is excited in measles, Leucocytes, 
"which begins soon after infection, reaches its 
maximum six days before the appearance of the 
eruption, and lasts into the first part of the stage 
of invasion" (Tiliston). We are ignorant of the 
significance of this phagocytosis. 

There is no serum therapy for measles. Weiss- 



immunization. 



562 



INFECTION AND IMMUNITY 



becker states that the serum of convalescents in- 
fluences the course of the disease favorably. 

XI. GERMAN MEASLES (ROTHELN). 

Eotheln is considered as distinct from measles, 
in spite of clinical similarities. It is recognized 
because of certain peculiarities in the eruption and 
its uniforrhly mild course. Perhaps the strongest 
reason for believing the two diseases to be distinct 
lies in the fact that an attack of rotheln does not 
leave an immunity against measles. 

Eotheln is contagious. Efforts should be made 
to prevent extension, as in measles, the methods of 
transmission being the same in the two diseases. 

XII. WHOOPING COUGH. 

Various protozoa (?) and bacteria (cocci and 
bacilli) have been assigned as the cause of whoop- 
ing cough. Many of the so-called protozoa found 
in the throat were undoubtedly tissue cells (leuco- 
cytes, ciliated epithelium). Among the cocci, the 
diplococcus of Eitter (1892) acquired some promi- 
nence. He is said to have found it constantly in 
146 cases. Investigations by others failed to jus- 
tify his conclusions. 
The influenza- Disregarding some other bacilli which certain 

like Bacillus of . , . , ■. , , , -. , -. . , -. 

Sprengierand investigators have attempted to bring into rela- 
o jochmann. ^- on w ^ pgj^^ggfg^ we mav no ^ e the essential facts 

concerning an influenza-like bacillus which has 
been found with great constancy and by many 
competent investigators in the sputum of patients. 
First observed by Sprengler (1897) in pertussis 
sputum, this organism or bacilli similar to it have 
been found by Czaplewski and Hensel, Zusch, 
Cavasse, Vincenzi, Elmassian, Luzzatto, Arnheim, 
Jochmann and Kruse, Eeyher, Smit. Wollstein, 



WHOOPIXG COUGH. 563 

and Davis. The organism is said to be somewhat 
larger and thicker than the true influenza bacillus, 
but has the same bipolar staining affinity and the 
same demand for hemoglobin for its growth in 
pure cultures. There is some difference of opinion 
as to whether the organisms described by these 
different observers are all identical and as to 
whether all have worked with pure cultures. The 
conclusion of Davis would seem to sum up the 
situation: "With the exception of Manicatide, 
probably all of the investigators, at least in more 
recent years, have been dealing, either in pure or 
impure cultures, with the influenza-like bacillus, 
first described by Sprengler and later by Joch- 
mann." Culturally they are not to be differ en- Hemophilic 
tiated from the influenza bacillus. When in pure and P fym* s 
culture they demand hemoglobin for their develop- b,os,s - 
ment, although the amount of hemoglobin may be 
so small as not to color the medium. When in 
mixed culture with the streptococcus, staphylo- 
coccus, pneumococcus and B. xerosis, they grow 
abundantly even in the absence of hemoglobin. 
Hence, in relation to symbiosis, also they resemble 
the influenza bacillus. For symbiotic development 
it is necessary that the secondary organisms be 
living; when killed or when the filtrates of bouil- 
lon cultures are used, the "pertussis bacilli" are 
not stimulated to growth. 

Inoculation Of pure Cultures On the mUCOUS Pathogenicity. 

membrane of the upper respiratory passages in 
various animals, including the monkey, does not 
produce a pertussis-like infection. The organisms 
have, however, a low degree of virulence for ani- 
mals, particularly the guinea-pig. Davis found 
that three blood-agar cultures injected intraperi- 



564 



INFECTION AND IMMUNITY. 



toneally killed guinea-pigs in 24 hours or less. 
The virulence of the organism is augmented when 
mixed with certain other bacteria. By injecting it, 
mixed with a non-pathogenic staphylococcus, its 
virulence, after six passages, was so increased that 
one blood-agar culture killed guinea-pigs in 24 
hours (Davis). In this respect, also, it resembles 
the influenza bacillus. 
significance. Inoculated in the throat of an adult, who pre- 
sumedly had never had whooping cough, a distinct 
febrile reaction, lasting two or three days, devel- 
oped after an incubation period of two days 
(Davis). Headache and pharyngitis were accom- 
paniments of the reaction and the pharyngitis 
continued for at least four weeks. There was lit- 
tle cough, and it was concluded that the micro- 
organism had not produced whooping cough, 
although it had shown toxic and infec- 
tious properties. The bacillus proliferated enor- 
mously in the pharynx and nose and was still to 
be cultivated after four weeks. Such an organism 
may well be an important factor in whooping 
cough, even though it is not the essential cause. 
Davis is inclined to regard its relation to whoop- 
ing cough as similar to that of the streptococcus 
to scarlet fever — i. e., a very important compli- 
cating organism. 

Davis finds still further reason for doubting its 
specific relationship to whooping cough from the 
fact that it was found frequently in measles, acute 
influenza, epidemic meningitis, bronchitis, vari- 
cella and in normal throats. 

The organism is disseminated extensively by 
coughing, and the same is probably true of the es- 
sential virus. Close contact, as by kissing, or the 



WHOOPIXG COUGH. 



5G5 



common use of eating utensils is a means of trans- 
mission. The opinion has been advanced by Weill 
and Pehn that pertussis is contagious only during 
the catarrhal stage of the disease. "Of ninety- 
three non-immune children who were placed with 
fifteen children who were in the convulsive stage, 
none became sick" (cited by Gotschlich). This 
point is not sufficiently established, however, to 
warrant modifications of prophylactic measures. 
Whooping cough is often epidemic and is more 
common in cities where contact with the infected 
is more likely to occur than in the country, The 
incubation period is from seven to fourteen days. 

Isolation is more difficult than in the more acute 
contagious diseases, yet contact with other chil- 
dren should be avoided as much as possible, and 
the patients should be withdrawn from school 
until recovery is complete. 

Pertussis is almost exclusively a disease of chil- 
dren, although older people may be attacked. Sus- 
ceptibility is not general. One attack usually con- 
fers immunity. A varying degree of leucocytosis 
is excited by the infection (12,000 to 45,000), the 
significance of which is not known. It is chiefly 
mononuclear. 

Serum therapy for whooping cough has not ad- 
vanced to a point where we can speak with as- 
surance concerning it. Manicatide (1903) im- 
munized horses and sheep with the organism which 
lie cultivated from a large number of cases. He 
reports that cure may be accomplished in from 
two to twelve days when the serum is used within 
the first fifteen days of the disease. The bacillus of 
Manicatide differs from the influenza-like organ- 
ism of other observers, hence, his antiserum can 



Contagious- 
ness. 



Serum 
Therapy. 



566 INFECTION AND IMMUNITY. 

not be accepted unreservedly as a specific serum 
for whooping cough. Smit found that an anti- 
serum for the influenza-like organism exerted no 
influence on the disease. 

XIII. MUMPS (EPIDEMIC PAROTITIS). 

Mumps occurs epidemically in children, particu- 
larly in schools, in other institutions, and in sol- 
diers confined to barracks. It is most frequent in 
the spring and autumn and probably is endemic in 
large centers of population. It is contagious, the 
virus probably being disseminated from the upper 
respiratory passages with infected droplets of spu- 
tum and saliva. The disease has an incubation 
period of two to three weeks and runs its course 
in from seven to ten days. 

Involvement of the testis, ovary or female breast 
are complications to be feared in adult life ; "orchi- 
tis, albuminuria, with convulsions, acute uremia, 
endocarditis and peripheral neuritis are occasional 
complications" (Osier). Fatal meningitis devel- 
ops rarely. Very young infants and adults are at- 
tacked less frequently than children of school age. 
Patients should be isolated for three weeks from 
the time symptoms appear (Gotschlich). 
One attack usually establishes protection. 
A peculiar form of parotitis sometimes follows 
injury of the abdominal and pelvic viscera, the so- 
called "postoperative" parotitis. The parotid 
glands may also be invaded by a number of known 
micro-organisms, e. g., the pneumococcus. 



cAPPENDIX. 



I. — The Hypothesis of Welch. 

What has come to be known as the hypothesis of Welch 
is of such practical and theoretical importance that ref- 
erence to it should not be passed over. It may be put 
in the form of the following question: If bacterial tox- 
ins and the constituents of bacterial cells so act on the 
tissue cells that the latter produce bodies (antibodies) 
which are inimical to the bacteria, why may not the 
body fluids in turn so act on the bacteria that the latter 
produce bodies (antibodies) which are inimical to the 
tissue cells? "Looked at from the point of view of the 
bacterium, as well as from that of the animal host, ac- 
cording to the hypothesis advanced, the struggle be- 
tween the bacteria and the body cells in infections may 
be conceived as an immunizing contest in which each 
participant is stimulated by its opponent to the produc- 
tion of cytotoxins hostile to the other, and thereby en- 
deavors to make itself immune against its antagonist." 
(Welch.) 

A more reasonable hypothesis could hardly be ad- 
vanced, and no small number of facts known at the pres- 
ent time are in harmony with it. Walker had already 
performed work of a fundamental character, which 
showed that the typhoid bacillus, when grown in the 
presence of its antiserum, acquires greater virulence for 
animals. Furthermore, a greater dose of protective 
serum was required to save guinea-pigs from infection 
with the immunized culture than from the same strain 
which had not been immunized. The fact has been known 
for a long time that the typhoid bacillus resists agglu- 
tination when freshly cultivated from a patient having 
the disease, whereas it becomes easily agglutinable after 
a period of artificial cultivation. It may well be assumed 
that the bacillus, when playing the part of an infecting 
organism, gradually was immunized against the agglu- 
tinating properties of the patient's serum: and, on the 



568 APPENDIX. 

other hand, that it lost tnis resistance after it had been 
removed from the stimulating influence of the infected 
body. This immunization with agglutinins may be car- 
ried on in the test glass, and bacteria which have been 
so treated acquire the power to absorb a greater quantity 
of agglutinin from the homologous serum (Bail). 

Another pertinent observation was that by Wechsberg, 
who found that a strain of the diphtheria bacillus when 
grown in a medium containing diphtheria antitoxin 
could ue made to produce diphtheria toxin more abund- 
antly. We may assume that the antitoxin combined with 
the corresponding receptors situated in the bacilli 
( diphtheria toxin ) , and that the bacilli were, as a result, 
stimulated to produce a greater number of such recep- 
tors (toxin). 

Consistent as these observations are with the hypo- 
thesis under discussion, Welch meant a great deal more 
than the immunization of the bacteria against the de- 
fensive powers of the animal body. Not only may a bac- 
terium during infection become more resistant to the 
bactericidal action of the body by producing antibodies 
for those bactericidal agencies, or by its ability to ab- 
sorb and dispose of a greater quantity of bacteriolysin ; 
and not only may a bacterium be able to respond to the 
presence of natural antitoxins in the body by the pro- 
duction of more toxin; but, in addition, certain constitu- 
ents of our body fluids may, by combining with suitable 
bacterial receptors, stimulate the bacterium to the pro- 
duction of a whole shower of cytotoxins, which attack the 
leucocytes, erythrocytes, nerve cells, liver, kidney, etc. 
The nature of the animal substances which may combine 
with the bacterial receptors and thus cause the formation 
of the bacteriogenic cytotoxins is left an open question, 
and is not of essential importance for the theory; it is 
not at all necessary that they be toxic for the bacterium, 
and they may even be taken up as food substances. 
Likewise the possible nature of the cytotoxins produced 
by the bacterium is of secondary importance. It so hap- 
pened that Welch assumed that they might be of the 
nature of amboceptors, which may become complemented 
by bacterial complement, by the circulating comple- 
ment of the body or by endocomplements of the tissue 
cells. One could with equal reasonableness assume that 



APPEXDIX. 5G9 

they may be complete toxins, receptors of the second 
order, with a haptophorous and a toxophorous structure. 

A well-known statement of Metchnikoff is to the effect 
that a particular bacterium when virulent is not so 
readily taken up by leucocytes as is an avirulent strain. 
This fact has been noted repeatedly in recent times in 
tne study of phagocytosis in the test tube. This may be 
because the organism, in its virulent parasitic state, 
secretes substances which repel the phagocytes, neu- 
tralize the opsonins, or because of the formation of 
actual leucocytic toxins. 

One of the most widely known phenomena in relation 
to the virulence of some organisms is that their patho- 
genicity may be increased by passing them through suit- 
able animals repeatedly. The best results are obtained 
when intermediate artificial cultivation is avoided and 
tne inoculations are made directly from the dead into 
the living animal. It may, with all reason, be assumed 
that by continued residence in the host the bacterium 
has been trained to produce a greater quantity of toxic 
substances which are inimical to the host, and that the 
increased virulence of the parasite depends on this con- 
dition. 

Although up to the present time systematic attempts 
to place the hypothesis of Welch on a firm experimental 
basis appear not to have been made, the observations 
cited, as well as others which could be enumerated, pro- 
vide cumulative evidence of its correctness. 

II. — The Aggressins of Bail. 

Not entirely foreign to the subject discussed above is 
the so-called aggressin theory of Bail, the essential points 
of which may be given without entering into a detailed 
discussion. 

Bail attributes to pathogenic bacteria the property of 
"aggressiveness," through which they directly antagonize 
the protective agencies of the body. The micro-organ- 
isms of highest parasitic powers, the "true parasites," 
as those belonging to the hemorrhagic septicemia group, 
possess the greatest aggressiveness, since they are able to 
proliferate in the blood stream while the antibacterial 
activities of the body (phagocytosis, etc.) are hold in 
abeyance. Other bacteria, which in causing disease tend 



570 



APPENDIX. 



to remain localized, and, if by any means they reach the 
blood stream, are not able to proliferate greatly in this 
place, are "half parasites" and have a lower degree of 
aggressiveness; they are more susceptible to phagocyto- 
sis and to the action of bacteriolysins (typhoid, cholera, 
dysentery ) . Saprophytes have no aggressive action. 

This is very general, but Bail and his co-workers have 
attempted to put the conception on an experimental basis 
by demonstrating the existence of a substance on which 
L^e aggressiveness of bacteria depends; to this substance 
they give the name of "aggressin.' 

Intraperitoneal inoculation of the tubercle bacillus 
into the guinea-pig leads to more or less general tuber- 
culosis and to the death of the animal in the course of a 
few weeks. If, during the course of the disease, a second 
injection of a large quantity of the bacillus is made into 
the peritoneal cavity, or if an injection of tuberculin is 
given, the animal dies very quickly. This is, of course, 
nothing more than the well-known hypersusceptibility of 
tuberculous animals to the products of the tubercle 
bacillus. In addition to this fact, however, a similar 
result was obtained in another manner. If a large quan- 
tity of bacilli is placed in the peritoneal cavity of a 
healthy guinea-pig, and the exudate is removed after 
twenty-four hours and freed from leucocytes and bacilli, 
the aggressin of the bacillus is said to be present in the 
clear fluid. This is demonstrated by injecting some of 
the fluid, together with' tubercle bacilli, into the peri- 
toneal cavity of another healthy guinea-pig. The rapid 
death of the animal is the result, whereas the bacilli 
alone cause death only after a long period, and the cell- 
free exudate alone is without toxicity. 

A similar condition has been found in experimental in- 
fections with a number of bacteria (typhoid, cholera, 
dysentery, plague, chicken cholera), the essential fact 
being the same: that, following intraperitoneal or intra- 
pleural inoculation, the resulting exudate, when freed 
from leucocytes and bacteria, has the power of intensify- 
ing an infection by the corresponding organism. 

There seems at present to be no definite knowledge 
concerning the nature of these aggressins, although Bail 
thinks they may resemble true toxins in some respects. 
Likewise the precise character of their action is un- 



APPENDIX. 571 

known, although Bail and his co-workers are strongly 
inclined to the view that they inhibit phagocytosis by 
some direct action of the leucocytes. 

It is further interesting that immunization with ag- 
gressins is said to give rise to the formation of anti- 
aggressins, and that by the use of antiaggressive serum 
the action of the aggressins is neutralized, and the bac- 
teria consequently become the prey of the leucocytes. 
The action of the antiaggressive serum is said not to 
depend on the presence of bacteriolysins. 

One can hardly attempt a serious criticism of the 
aggressin theory at this time, and the above statements 
are made onlv to signify its general character. 

III. — COBRA-LECITHID. 

Too late to be incorporated in its proper place in the 
text, it is learned that the chemical identity and mole- 
cular weight of cobra -lecithid have been determined by 
Dr. Kyes in the laboratory of Ehrlich, and that work 
descriptive of the characteristics of the substance is in 
process of publication. 



"BIBLIOGRAPHY. 



Hop!; : Inimunit : it und Immunisierung, Tubingen, 1902. 

Ehrlich (and his pupils) : Collected Studies on Immunity. 
Authorized Translation by Charles Bolduan, M. D. (In prep- 
aration). John Wiley & Sons, New York. 

Metchnikoff : Immunity in Infective Diseases, Masson et 
Cie., Paris, 1001. Translated bv Binnie. MacMillan & Co. 
$5.25 net. , 

Dieudonne : Immunitat, Schutzimpfuhg und Serumtherapy. 
4th Edition. Joh. Ambr. Barth, Leipzig, 1905. (Gives the 
fundamental literature.) 

Roger : Les Maladies Infectieuses. Masson et Cie., Paris, 

1902. (Detailed treatise on the infectious properties of 
different micro-organisms.) 

Kolle and Wassermann : Handbuch der Pathogen en Mi- 
kro-organismen, Gustav Fischer, Jena, 1902-1904. Four 
volumes. 

Ritchie : Current Theories of Immunity. Journal of Hy- 
giene, 1902, pp. 215, 252, 344. 

Charrin : Les Defenses Naturelles de l'Organisms. Masson 
et Cie., Paris, 1898. 

Bosanquet : Serums, Vaccines and Toxins. Keener & Co., 
Chicago, 1904. 344 pages. 

Oppenheimer, Carl : Toxine und Antitoxine, Fischer, Jena, 
1904. (Gives the important literature.) 

Wassermann : Immune Sera, Hemolysins, Cytotoxins and 
Precipitins. Translated by Charles Bolduan, 1904. 

Sachs : Die Hemolysins From Lubarsch-Ostertag's Er- 
gebnisse\ Bergmann, Wiesbaden, 1902. (Literature to date of 
publication is given. Reprint may be purchased.) 

Sachs : Die Cytotoxine des Blutserums. Biochemisches 
Centralblatt, i, 1903, 573 ff. (Literature to date of publi- 
cation.) 

Bensaude : Le Phenomene de l'Ag&lutination des Mi- 
crobes. Paris, Carre et C. Naud, 1897. (Gives the early 
literature on agglutination.) 

v. Dungern : Die Antikorper. Fischer. Jena. 1903. 

Weigert. E. : Les Tuberculines. Storck et Cie., Lyon, 
France, 1902. 

Wright : A Short Treatise on Antityphoid Inoculation. 
Archibald Constable, Westminster, 1904. (An exposition of 
the methods and principle's of Wright.) 

Scheube : Diseases of Warm Countries. Second Edition, 

1903. Translated by Cantlie. 

Manson : Lectures on Tropical Diseases. Chicago. Keener 
& Co.. 1905. 

Nocard and Leclainche : Les Maladies Microbienne des 
Animaux. Two volumes, third Edition. Masson et Cie., 
Paris. 1905. 

Welch : The Huxley Lecture on Recent Studies of Im- 
munity with Special Inference to Their Bearing on Path- 
ology. Medical News, 1902, vol. Ixxxi, 721. 



* See note in the Preface concerning Bibliography. 



INDEX. 



FAGE. 

Abrin 6., 104, 204 

Achalme, bacillus of, in rheumatic fever 359 

Acne, staphylococcus in 376 

Acquired immunity (see Immunity, acquired). 
Active immunity (see Immunity, active). 

Actinomyces oovis et hominis (ray fungus) 10, 458 

Classification of, 459, 460 ; cultivation and morphology 
of, 459 ; lungs, in, 337 ; occurrence of, in nature, 
460 ; phagocystosis of, 461 ; resistance of, 459 ; 
species of, and virulence of, 460. 

Actinomycosis 10, 450-462 

Animals, susceptibility of, to. 460 ; connective tissue, 
formation of, in, 5, 458, 461 ; immunity and sus- 
ceptibility to, 461, 462 ; infection atria, 460 ; iodid 
of potassium in treatment of, 462 ; lesions, charac- 
ter of, 458, 460 ; phagocytosis in, 461 ; prophylaxis 
of, 461 ; transmission of, 460. 
Acute articular rheumatism (see Rheumatic fever) .... 541 

Adrenal gland, cytotoxin for 173 

Agglutination 92, 118 

Of erythrocytes, 103 ; of erythrocytes with silicic acid, 
129 ; etiology, determined by, 7 ; group agglutina- 
tion. 110, 113 ; immunity, relation to, 96, 97 , 
macroscopic and microscopic, 102 ; prognostic im- 
portance of, 95 ; sodium chlorid, influence on, 110 ; 
stages in the reaction, 110 ; substances concerned, 
105 ; serum dilutions, 113 ; specificity, 111 ; technic, 
98 ; theories of mechanism of, 116 ; see also \inder 
Agglutinins and under different diseases and micro- 
organisms. 

Agglutinins 92-118 

Absorption of by bacteria, 203 ; agglutinophorous 
group, i08 ; autoagglutinins, 104 ; chief agglutinins, 
111; congenital, 93, 96; definition, 105; distribution 
of, in the body, 95 ; Ehrlich's theory of the produc- 
tion of, 114; ferments, action of, on, 96, 107; for- 
mation of, following vaccination, 233 ; haptophorous 
group of, 108 : Hauptagglutinin, 111 ; immune, 62, 
it:') ; isoagglutinins, 104 ; mixed infections, influence of, 
on. 113; Mitagglutinin, 109; normal, 55, 92; origin 
of, 90 ; precipitation of, by chemicals, 107 ; produc- 
tlon of, 93: receptors of 2d order, 108; resistance 
to acids and alkalies, 109 ; resistance to heat, 97, 
108, 109 ; somatic and flagellar, 107 ; specificity of, 
92 ; structure of, 108 ; union with cells, character 
of, 203, 204 ; unit of measure of, 103 ; variations 
of, in animals, 114 ; variations in the quantity of, 
95; zymotoxic group of, 108; see Agglutination, 
Agglutinogens, Agglutinoids, and also under the dif- 
ferent micro-organisms. 



574 INDEX. 

PAGE. 

Agglutinogens power of bacteria 94 

Agglutinogens, or agglutinable substances 105 

Diffusibility of, 107; distribution of, 106; flagellar 
and somatic, 107 ; multiplicity of, 107 ; resistance of, 
to heat, 107 ; structure of, 108 ; see Agglutinins 
and Agglutination. 

Agglutinoids 109 

Aggressins 569 

Alexins 49, 130 

Definition of, 49 ; identity of, with complement, 134, 
135 ; nature and selective action of, 131 ; see Com- 
plement. 
Alkaloids. 

Failure to cause formation of antibodies, 198 ; state 
of, within the' cells, 198, 205. 

Amboceptoid, 209 

Amboceptors 134, 141 

Absorption of, by cells, 144, 146, 203 ; bacteriolytic, 
143 ; complementophilous haptophore of, 147 ; cyto- 
philous haptophore of, 146 ; formation of, 150 ; for- 
mation following vaccination, 233 ; hemolytic, 141 ; 
influence in phagocytosis, 190 ; isolation of, 146 ; 
manner of action of, with complement, 145, 148, 207, 
208 ; occurrence of, in animal secretions, 158 ; origin 
from leucocytes, 183, 190 ; origin in cholera, 190 ; 
receptors of the 3d order, 207 ; sensitization by, 142, 
145 ; solutions of, 144 ; specificity of, 152, 153 ; 
structure of, 147 ; synonyms for, 148, 217 ; union 
with cells, nature of, 147, 148, 203, 204 ; see Hem- 
olysins (serum), Bacteriolysins, Cytotoxins and 
Venoms. 
Ameba coli. 

Discovery of, 502 ; pathogenicity of, 502 ; symbiosis of, 

502 ; see Amebic dysentery. 

Ameba proteus 500 

Ameba. 

Cultivation and distribution of, 501 ; phagocytic action 
of, 176 ; resistance of, 501 ; symbiosis, 501, 502. 

Amebic dysentery 500 

Anatomic changes in, 503 ; immunity to, 504 ; liver 
abscess in, 503 ; occurrence of, 502 ; prophylaxis, 

503 ; see Amebse, and Ameba coli. 

Amibodiastase 176 

Amyloid degeneration, production of by staphylococcus. . 375 

"Anatomic tubercle" (see Tuberculosis j. 

Animals, susceptibility of, to 

Actinomycosis, 460 ; anthrax, 330, 331 ; B. influenzae, 
394 ; B. melitensis, 335 ; cholera, 309 ; hydrophobia. 
513, 514 ; leprosy, 447 ; Micrococcus catarrhaUs, 
384 ; Micrococcus meningitidis, 390 ; oidiomycosis, 
467 ; pneumococcus, 339 ; pseudotuberculosis, 444 ; 
relapsing fever, 404 ; staphylococcus, 375. 378 ; 
streptococcus, 352 ; syphilis, 522 ; trypanosomiasis, 
490, 495 ; tuberculin, 414 ; tuberculosis, 427, 441. 

Animal experiments, in testing value of serums 201 

Anopheles mosquitoes. 

A. maculipennis, 478 ; A. punctipennis, 478 ; habits 
of, 478 ; life cycle of. 478, 479 ; malaria, role in, 
468 ; migration of, 479 ; occurrence. 478. 



INDEX. 575 

PAGE. 

Anthracase-Immuupioteidin 332 

Anthrax 327-333 

Animals, immunity and susceptibility of, 330, 331 ; 
bacillemia, 330 ; discovery of its microbic nature, 
27, 28, 29 ; immunity, 332 ; immunization, mixed, 
333 ; influence of streptococcus on, 362 ; malignant 
pustule, 329 ; occurrence, 327 ; opsonins, 331, 333 ; 
phagocytosis in, 190, 331 ; prophylaxis, 330 ; serum- 
therapy, 332 ; toxic results, 330 ; transmission, 329 ; 
vaccination, 28, 29, 332 ; wool-sorters' disease, 329 ; 
see also B. anthracis. 

Antiabrin 90 

Antiaggressins 571 

Antiamboceptors 156 

Danger in formation of, 157 ; as receptors of the first 
order, 207. 

Antibacterial serums (see Bacteriolysins) 226-231 

Antibodies. 

Mechanism of production, 199 ; origin of, 210, 314 ; 
scheme of, 216 ; specificity of, 208 ; union with 
antigens, 200 ; see Antitoxins, Amboceptors, Ag- 
glutinins, Precipitins, Hemolysins, Bacteriolysins and 
Cytotoxics. 

Anticomplements 154, 207 

Anticrotin , 90 

Anticytotoxins 165 

Antiferments 63, 90 

Antigens. 

Scheme of, 216 ; union with tissue cells, character 
of, 200. 

Antiglobulin 124 

Anti-immune serum 156 

Antilaccase 90 

Antileucocidin 90, 372 

Antileucotoxic serum 169 

AnMnephrotoxin 170 

Antineurotoxin 171 

For venom, 266. 

Antipepsin 90 

Antiprecipitins 123 

Antirennet 90 

Antiricin 90, 201, 202 

Antirobin 90 

Antisperrcotoxin 166 

Antistaphylolysin 380 

Antisteapsin 90 

Antistreptolysin 353 

Antitoxins 65, 91, 221, 235 

Earlv administration of, 223, 224 ; curative action of, 
222, 223 ; discovery of, 33 ; examination of by U. S. 
* Hygienic Laboratory, 76; for animal toxins, B0; 
for li. botulinus, 359; for B. diphtheria:, 241. 243; 
for fi. i>i/oryaneu8, 260, 261; for B. ietaui, 223, 
252 : for hacterial toxins, 89, 90 ; for plant toxins 
(abrin. crotin, ricin, robin, phallin), 90, 264: for 
pollen toxin, 263; for zootoxins, 268; formation of. 
85; liuptophorous group of. 79; Infections charac- 
terized by tho formation of, 235. 268 . leucocytic 



570 INDEX. 

PAGE. 

origin, question of, 191 ; manufacture of, 69 ; mode 
of action of, 201, 221, 226 ; nature of, 191 ; toxins, 
neutralization of, by, 78, 201, 203 ; normal, 45 ; pres- 
ervation of, 71, 73 ; prophylactic action of, 226 ; 
receptors, free, 89 ; receptors of the first order, 207 ; 
relation of, to toxins, in the body, 222 ; rela- 
tion of, to toxins, in vitro, 221 ; standardization of, 
72, 255 ; unit of, 72 ; see Part II, Group 1, and also 
the different micro-organisms. 

Antitrypsin 90 

Antiurease 90 

Antivenin 70, 90, 267, 268 

Antityrosinase 90 

Arachnolysin (spider poison) 16, 268 

Arrhenius and Madsen, views of 210 

Arthritis 344, 348, 354, 378, 386, 391 

Aspergillus . 6, 467 

Atrophy, phagocytosis in 178, 179 

Attenuation. 

Importance' of in vaccination, 57 ; methods of, 219. 

Autoagglutinins 104 

Autocytotoxins 163, 174 

Autolytic products, vaccination with 220, 312 

Autonephrotoxins 169 

Autoprecipitins 121 

Autospermotoxin 166 

Bacillus aerogenes capsulatus 14, 185, 359 

Bacillus alcaligenes 270 

Bacillus anthracis 10, 327-329 

Antagonism of, by other bacteria, 329 ; antiserums for, 
32 ; attenuation of, 58, 219 ; cultivation of, 328 ; 
discovery of, 27, 327 ; gastric juice, effect of, on, 39, 
329 ; immunity, active, 332 ; immunity, acquired, 
186, 331 ; immunity, natural, 330 ; immunity, 
passive, 332 ; infection atria, 39 ; opsonins, 331 ; 
phagocytosis of, 331 ; serums, effect of, on, 48, 49, 
331 ; spores of, 29, 327, 328 ; toxic properties of, 
330 ; vii'ulence of, 329 ; see Anthrax. 

Bacillus J)Otulinus 256, 257 

Animals, susceptibility of, 257, 258 ; antitoxin for, 
259 ; morphology, etc., 257 ; occurrence in meat, 
257 ; saprophytic nature of, 258 ; spores of, 257 ; 
toxin, action of, 258 ; toxin, detection of in meat, 
257 ; toxin, preparation and resistance of, 258 ; 
see Botulism. 
Bacillus chancri mollis (bacillus of Ducrey ; bacillus 

of soft chancre) ' 16, 399 

Cultivation, morphology, phagocytosis of, susceptibil- 
ity of animals to, 400. 

Bacillus of chicken cholera 58 

Bacillus coli communis 298-3*04 

Agglutination of, 92, 94, 111, 304 ; autagonism for pu- 
trefactive bacteria, 299, 300 ; antiserums, properties 
of, 303 ; beneficial functions of, 299 ; in cystitis. 303 ; 
in enteritis, 40, 301, 303; group agglutination, 111; 
group of, 298 ; in meningitis, 389 ; morphology and 
staining of, 298 ; occurrence in intestines, 298, 299 ; 
occurrence in nature, 298 ; in pneumonia, 336 ; re- 



IXDEX. 577 

PAGE. 

sistance of, 298, 299 ; serums, effect of, on, 299 ; sym- 
biosis with Ameba coli 3 502 ; toxin of, 303 ; typical 
strains of, 299 ; virulence of, 300, 301, 302. 

Bacillus diphtheria) 10, 235, 236 

Agglutination of, 243 ; antitoxin for, 89, 241, 242 ; 
morphology, staining, cultivation, resistance, viabil- 
ity of, 236 ; occurrence of, in the body. 237, 238 ; 
phagocytosis of, 240 ; pneumonia, in, 336 ; toxic ac- 
tion of, 15 : toxins of, 66, 67, 237, 238, 242 ; toxin, 
attenuation of, 40, 219 ; tuberculosis, in, 425 ; 
see Diphtheria. 

Bacillus of Ducrey. See Bacillus chancri mollis. 

Bacillus dysentericv 10, 288-290 

Agglutination of, 92, 94, 288, 289, 294 ; antiserums 
for, properties of, 293 ; cultivation and morphology 
of, 288, 289 ; dissemination of, 292 ; endotoxin of, 
291 ; etiologic role of, 289 ; "Flexner" type of, 289 ; 
pseudodysentery bacilli, 288 ; toxicity of, 291 ; toxin, 
autolytic, of, 291 ; types of, 288 ; see Dysentery, 
acute epidemic. 

Bacillus edema; maligna:- 1, 14 

Bacillus enteritidis 294-298 

Agglutinins and agglutination of, 94, 298 ; Bacillus 
paratyphosus, resemblance to, 285 ; discovery of, 
295 ; fermenting powers of, 295 ; group agglutina- 
tion, 111 ; group of, 295 ; meat poisoning by, 
294-298 ; morphology and staining of, 295 ; occur- 
rence of, in meat of horses and cattle. 295, 296, 
297 ; poisoning by oysters and fish, in, 297 ; resist- 
ance of, 297 ; toxin, 295-296 ; toxin, occurrence in 
meat, 297 ; toxin, resistance of, 297. 

Bacillus of Friedlander : see Bacillus pneumonia. 

Bacilli from butter, grass and milk 444 

Bacillus icteroides, in yellow fever 11, 530, 531 

Bacillus influenza} 10, 394 

Agglutination of, 399 ; animals, virulence for, 395 ; 
antiserum, properties of, 399 ; in conjunctivitis, 
396 ; cultivation of, 394 ; discovery of, 394 ; excre- 
tion of. 395 ; hemophilic properties of, 394 ; im- 
munization with, 399 ; in meningitis, 389-396 ; 
morphology and staining of, 394 ; occurrence of. in 
the' body. 396 ; otitis media, in, 396 ; peritonitis, in, 
396 ; resistance of, 39. r . ; symbiosis of, 394 : loxin 
of, 395 ; tuberculosis, in, 425 ; see Influenza. 

Ba(illus lactie airofjenes. 

Antagonistic action on putrefactive bacteria, 300 ; oc- 
currence in intestines, 401. 

Bacillus lepras 10, 446 

Animals, insusceptibility of. to, 447 ; antiserums for. 
452; discovery of, 446; endotoxin, question of. 450; 
excretion and occurrence in nature of. 447 ; ineul- 
tivability of, 447 ; morphology of, 447 ; occurrence 
in the body, 449; phagocytosis of, 449, 451; see 
Leprosy. 

Bacillus of Lustgarten 443, 552 

Bacillus mallei 10. 453 

Agglutination of, 458 ; cultivation, morphology and 
resistance of. 453 ; mallein, varieties, and prepara- 



INDEX. 



PAGJL 

tion of, 454 : meningitis, in, 389 ; phagocytosis of, 
456. 

Bacillus melitensis 334, 335 

Agglutination of, 334 ; animals, susceptibility of, to, 
335 ; morphology of, 334 ; opsonins, influence of in 
phagocytosis of, 334 ; serums, effect of, on, 334 ; 
see Malta fever. 

Bacillus mucosus capsulatus 401 

Bacillus of ozena 402 

Bacillus varatyphosus 284 

Agglutination of, 11, 284, 287 ; antiserums for, prop- 
erties of, 287 ; blood cultures, 288 ; endotoxin, 287 ; 
excretion of, 286 ; meat poisoning by, 285 ; occur- 
rence in the body, 286 ; "paracolon" bacilli, rela- 
tion to, 285 ; resistance of, 286 ; toxicity, 287 ; 
types of, 285 ; see Paratyphoid fever. 

Bacillus pestis 10, 316-319 

Agglutination of, 94, 326; cultivation of, 316, 317; 
endotoxin, resistance of, 319 ; excretion of, 321 ; 
involution forms, 317 ; meningitis, in, 389 ; mor- 
phology, 316; phagocytosis of, 325; pleomorphism, 
316 ; pneumonia, in, 336 ; resistance and viability, 
317, 318 ; staining of, 316 ; toxicity of cell bodies, 
319 ; toxin of Lustig and Galeotti, 318 ; toxin, 
soluble, question of, 318 ; virulence, 318, 319 ; 
see Plague. 
Bacillus pneumonias (bacillus of Friedlander) . 337, 401, 402 
Agglutination of, 94, 402 ; antagonism for B. anthra- 
cis, 329 ; antiserum, 402 ; influenza, 397 ; lesions 
caused bv, 402 ; meningitis, in, 389 ; pneumonia, in, 
336, 344. 402 ; tuberculosis, in, 425. 
Bacillus prodigiosus. 

Antagonism for B. anthracis, 329 ; Coley's mixture, in, 
362 ; symbiotic action of, 185. 

B.acillus psittacosis, agglutination of 94, 111 

Bacillus pseudotuberculosis, varieties of 445 

Bacillus pyoeyaneus 259-261 

Agglutination of, 92, 94 ; agglutinins for, 261 ; agonal 
invasion by, 259 ; antagonism for B. anthracis, 329 ; 
antitoxin, 261 ; bactericidal serum for, 261 ; fer- 
ments of, 260 ; endocarditis, in, 259 ; endotoxin of, 
260 ; enteritis, in, 40 ; infections, symptoms of, 
260 ; meningitis, in, 259 ; pigments of, 260 ; pyo- 
cyanase, 260 ; pyocyanolysin, 260 ; pyocyanin, 360 ; 
secondary infections by, 259 ; septicemia, in, 259 ; 
toxic action of, 16 ; toxin, soluble, 66, 260, 261 ; tu- 
berculois, in, 425. 

Bacillus of rhinoscleroma 402 

Bacillus of symptomatic anthrax 185 

Bacillus teiani 244-256 

Agglutination, 256 : anaerobic property of, 247 ; ani- 
mals, susceptibility of, to toxin, 51 ; avirulent 
strains, 249 ; discovery of, 244 ; morphology, stain- 
ing, cultivation, 244. 245 ; occurrence in intestines. 
246 ; occurrence in nature, 245 ; parasitic power of, 
247 : pathogenic properties of. 249 ; resistance of 
spores of, 246 : toxins of, 15, 20, 66, 67, 249 ; toxin, 
absorption of, by leucocytes, 191 ; toxin, fixation of, 



INDEX. 579 

PAGE> 

by tissues, 52, 53. 204, 205. 222, 251 ; toxin, 
attenuation of, 219 ; toxin, action of gastric juice 
on, 39 ; toxin, neutralization of, by antitoxin, 224 ; 
action of pancreatic juice on, 40 ; virulence, 185 ; 
see Tetanus. 

Bacillus tuberculosis 10, 407 

Agglutination, 438, 440 ; agglutination, relation of 
to immunity, 97 ; animals, susceptibility of to, 427 ; 
antiserums, properties of, 438 ; attenuation of, 
410 ; avian, 442 ; bacteria resembling, 443 ; bovine, 
differentiation of bovine, from human, 417 ; con- 
stituents, 411 ; cultivation, 409 ; discovery of, 
407 ; effect on tissues, 42, 44, 422-425 ; ex- 
cretion of, 414, 415, 419 ; fever producing 
substance of, 411 ; of fish, 443 ; gastric juice, re- 
sistance to, 39, 410 ; immunization with, 411, 430- 
432 ; inflammation of lungs, in, 337 ; lesions pro- 
duced by, 411 ; morphology of, 408 ; occurrence in 
nature, 414 ; pathogenic properties of, 411 ; pha- 
gocytosis of, 421, 422 ; proteins in, 411 ; resistance 
of, 409 ; staining properties of, 408, 411 ; strepto- 
coccus, influence of. on cultures, 350 ; "toxalbumin'' 
of, 411 ; toxic substances, effects of, 411 ; toxin of 
Marmorek, 404 ; toxins, 439, 440 ; virulence of, 
410, 427 : see Tuberculosis. 

Bacillus typhosus 10, 269 

Agglutination of, 92, 94, 116, 283, 284 ; antitoxin, 
question of, 271 ; autolysis of, 271 ; blood cultures 
of, 273, 284 ; discovery of, 269 ; dissemination of. 
270 ; endotoxin, 271 ; excretion of, 273, 274 ; ex- 
tracts of, 282 ; gastric juice, action of, on, 39 ; im- 
munization with, 280, 281, 283 ; leucocytes, relation 
of, to, 277 ; meningitis, in, 389 ; morphology of, 269 ; 
occurrence in body, 9, 270, 274 ; occurrence in na- 
ture, 270 ; phagocytosis of, 274 ; pneumonia, in, 336 ; 
resistance of, 270 ; symbiosis with Ameba coli, 502 ; 
toxin of Chantemesse, 282 ; vaccines, 279, 232 ; 
see Typhoid fever. 

Bacillus xerosis 244 

Bacterium coli commune; see Bacillus coli communis. 

Bactericidal serum, substance, etc. ; see Bacteriolysins. 

Bacteriolysins 130 

Absorption of. by bacteria, 136 ; composition of, 134 ; 
curative value of, 227, 231 ; endotoxins, action on, 
136, 228; group reaction with, 135; immunity, 
relation of, to, 135 ; inactivation and reactivation of, 
133, 134 ; nature and selective action of, 131 ; ori- 
gin of, from body cells, 45, 138; properties, general, 
130; prophylactic value of, -'2.1 ; specificity of, 135; 
standardization of, 138; technic of testing, 139; 
therapeutic use of, 220; see Amboceptors and Com- 
plements. 

Bacteriolysis and bacteriolysis 130 

Bacteriolysis. 

Group reaction, 153; mechanism of, 145; Pfeiffer's 
phenomenon. 181; similarity to hemolysis, 134; 
see Bacteriolysins. 

Bacteriolytic enzymes, relation to Immunity 61, 62 



580 



INDEX. 



PAGE. 

Bacteriotropic substances 227, 346, 309, 381 

BalanUdium coli, morphology, occurrence and patho- 
genicity 505, 506 

BalanUdium minutum 506 

Benzol ring ; use of, as an analogy in Ehrlich's theory 

196. 
Bile. 

Bactericidal and antitoxic properties of, 40 ; immune 
agglutinins in, 95. 
Biologic test for species ; see Precipitins. 
"Black Death" ; see Plague. 

"Blackwater fever" in malaria 477 

Blastomycetic dermatitis ; see Oidiomycosis. 
Blastomycosis ; see Oidiomycosis. 

Blue pus 259 

Bodo urinarius 508 

Botulism 16, 256-259 

Absorption of toxin, 258 ; antitoxin, 90, 259 ; immun- 
ity, 259 ; infected meats, 256, 257 ; phagocytosis, 
258 ; prophylaxis, 259 ; susceptibility, 258 ; symp- 
toms, 256 ; tissues affected by toxin, 258 ; see 
Bacillus botulinus. 

Bovine pest 11 

Bronchitis. 

In epidemic cerebrospinal meningitis, 391 ; meningo- 
coccus in, 391 ; Micrococcus catarrhalis in, 384, 
391 ; staphylococcus in, 377 ; streptococcus in, 354. 

Capsulated bacilli 401, 402 

Carbuncle, staphylococcus in 376, 377 

Carcinoma, hereditary susceptibility to 18 

Cell receptors ; see Receptors. 

Cercomonas intestinalis, morphology and pathogenicity 

of 506, 507 

Chancroid ; see soft chancre. 

Chemicals in relation to antibody formation 198 

Chemotaxis 43, 44, 177, 185 

Chicken cholera, attenuation of microbe of 219 

Chicken pox (varicella) 555, 556 

Chicken typhus or chicken-pest 11 

Cholera 10, 304-315 

Accidental, in man, 313 ; agglutination reaction, 315 ; 
animals, susceptibility of, to, 309 ; anti-bodies, 
origin of, 190, 314 ; antitoxic serum, 315 ; bacteri- 
cidal power of body fluids, 313 ; "cholera-carriers," 
304, 313 ; diagnosis, bacteriologic, 315 ; epidemiol- 
ogy, 307, 308, 311, 312 ; experimental, in man, 313 ; 
gastric juice, protective action of, 313 ; geographic 
distribution of, 307, 308 ; immunity and susceptibil- 
ity to, 56, 60, 190, 313, 314 ; infection atrium, 
307 ; lesions, intestinal, 310 ; effect of leucotoxic 
serum on infections, 168 ; mechanism of intoxi- 
cation, 310 : mixed immunization in, 234, 314 ; phag- 
ocytosis, 188, 189, 313, 314 ; phagolysis, 188 ; proph- 
ylaxis, 218, 307, 311 ; serum properties in, 20, 97 ; 
serum therapy, 230, 314, 315 ; sources of infection 
and transmission, 307-309 ; vaccines and vaccina- 
tion, 58, 312, 313 ; see Vibrio choleras. 

Cholesterin, neutralizing action on tetanolysin 91 

Chromophages 179 



INDEX. 581 

FAGE. 

Cladothrix, infections with 463 

Clavelee (sheep-pox) 11, 554 

Co-agglutinins '. . . Ill 

Cobra-lecithid 160, 206, 571 

Cobra venom ; see Venoms. 

Coccidia, life cycle, morphology, spore formation and 
pathogenicity, 508, 509. 

Coccidiosis SOS. 509 

Coccidium bigeminum 509 

Coccidium cuniculi s. ovifortne 509 

Cocobacteria septica (Billroth ) 349 

Coley s mixture 362 

Colle's law ; see Syphilis. 

Colloids 127, 128 

Complement. 

Absorption of, 145. 229 ; decrease of during disease. 
230: diversion of, 157, 229. 230; isolation of. 140; 
lecithin as a. 100 : multiplicity of, 153. 210 ; origin 
of, 138. ISO ; neutralization of. by salts, 91, 161 ; 
receptors of second order, 207 ; resistance to heat. 
134 ; solutions of. 144 : sources of, for bactericidal 
serums, 228, 229 ; specificity of, 152 ; structure of, 
149 ; unicity, theory of. 210 ; see Cytase. 
Complemintophilous haptophore ; see Haptophore. 

Complementoid 149, 209 

Complemaitoirt-Yerstopfitng 150 

Conjunctivitis. 

B. wftuenzix, in, 396, 397 ; diphtheritic. 237 ; menin- 
gococcus in. 391 ; pneumococcus in, 348, 349 ; 
staphylococcus in, 377. 

Connective tissue, role of. in inflammation 5. 42, 46 

Contact infection 3 

Contagion and contagiousness 2 

Contagious disease, definition 2 

Copula of Muller. synonyms for 148 

Cow pox 550, 554 

Crotln 104. 264 

Crystalloids, properties of 127 

Culex fatigons 540 

Culex pipiens. in transmission of malaria of birds.... 483 

Curative injections 220 

L'yclaster scarlatinalis 556 

See Scarlet fever. 

Cystomonas urinarius 508 

Cytase 1 78. 181, 182 

See Complement. 

< ytorycte* va\ iairr .-<. vaccina 543 

Conjugation, 544, 545 ; cytoplasmic stages. 544 ; life 
history of, 54-540; nuclear stau r t'-;. ~>44 ; smallpox, 
in, 543 ; vaccinia, in, 545. 

Cytotoxina (Cytolyslna) 55. 62. 162-175 

Activity, determination of, 164 ; amboceptors in, 165 ; 
antileucotoxin, 169; antinephrotoxin. 170; anti- 
Bpcrmotoxin, 166; autocytotoxins, 163. 174; auto- 
nephrotoxins, 169 ; autospermotoxin, 160 ; ciliated 
epithelium, cytotoxin for, 167 ; complements in, 
165 ; for malignant tumors, 164 ; hepatotoxins, 171 ; 
infections, effect of leucotoxins on, 168 ; leucotoxiu, 



582 INDEX. 

PAGE. 

167 ; nephrotoxic 169 ; neurotoxins, 171 ; origin, 
180 ; of venoms, 265, 266 ; pancreotoxin, 173 ; 
specificity, lack of, 162 ; spermotoxin, 165 ; structure 
of, -165 ; syncytiotoxin, 171 ; technic of production, 
164 ; thyrotoxin, 173 ; utility, theoretical, 162, 168. 
Cytolysins ; see Cytotoxins. 

Dacryocystitis, pneumococcus in 348 

Daphnia, phagocytosis of 183 

Dengue fever 539, 541 

Characteristics of, 546 ; contagiousness of, 540, 541 ; 
Culex fatigans in transmission of, 540 ; etiology, 
540 ; occurrence, 539 ; '"plasmeba" in, 540 ; recur- 
rences and relapses, 541 ; susceptibility to, 541 ; 
transmission, 540. 

Desmon 148 

Deuterotoxin 83. 209 

Diphtheria . 10. 13, 20, 235-244 

Agglutination reaction, 243 ; bacilli, localization of, 
238 : conjunctivitis, diphtheritic, 237 ; forms of, 

237 ; immunity and susceptibility, 56, 61, 239, 240 ; 
infection atria, 237 ; latent, 237 ; leucocytes in, 240 ; 
mixed infections in, 14, 238, 186, 358 ; paralysis, 
influence of antitoxin on, 242 ; predisposing causes, 
240 ; pneumonia in, 344 ; prophylaxis, 240, 241 ; 
pseudodiphtheria bacilli in, 243 ; recurrences, 56, 
240 ; septic, 239 ; serum therapy, 225, 241 ; sources 
of infection, 236, 237 ; tissues injured by toxin, 

238 ; transmission, 237 ; vulva, of, 237 ; see Bacillus 
diphtherial. 

Diplococcus intracellulars meningitidis ; see Micrococcus 
meningitidis. 

Diplococcus pneumoniae 336-349 

Agglutination of, 347 ; alveolar abscess, in, 348 ; ani- 
mals, susceptibility of, 339 ; antiserums, properties 
of, 346 ; conjunctivitis, 348, 349 ; dacryocystitis, 
348 ; discovery of, 337 ; endotoxins, 339 ; enteritis, 
348, 349 ; group agglutination, 348 ; immunization 
with, 345, 346, 347 ; influenza, in, 397 ; meningitis, 
348, 349, 389 ; morphology, staining, and cultiva- 
tion, 337, 338 ; neurotoxic strains of, 339 ; occur- 
rence in blood, 343 ; occurrence, normal, 339 ; op- 
sonins in phagocytosis of, 346 ; otitis media, in, 
348, 349 ; peritonitis, in, 348, 349 ; phagocytosis of, 
316 ; pneumonia, in, 337-348 ; pneumotoxin, 339, 
346 ; pulmonary hemorrhage, in, 344 ; resemblance 
to streptococcus, 338 ; resistance, 338 ; rhinitis, 
in, 348 ; septicemia. 348 ; serpent ulcer, 348, 349 ; 
tuberculosis, in, 425 ; virulence, 338 ; virulence, in- 
crease of, 342 ; see Pneumonia. 

Diplococcus (streptococcus) in rheumatic fever 359 

Dourine ; see Trypanosomiasis in animals. 

Droplet infection 237 

In diphtheria, 237 ; in influenza, 397 ; in tuberculosis, 
415. 

Drug habituation 22 

Dust infection 237 

In diphtheria, 237 ; in influenza, 397 ; iu tuberculosis. 
415; in typhoid fever, 272. 



IXDEX. 583 

PAGE. 

Dysentery, acute epidemic 8, 10. 288-294 

Agglutination reaction, 294 ; antiserums, properties 
of, 293 ; bacilli, dissemination of, by stools, 292 ; 
bacilli, distribution of, in the body, 290 ; chronic, 
288, 292 ; immunity and susceptibility, 60, 292, 
293 ; incubation period. 288 ; institutions, occurrence 
in, 292 ; intestinal lesions in. 290 ; occurrence of, 
288 : predisposing causes of, 292 ; prophylaxis, 292 ; 
serum therapy, 293 ; summer diarrheas of infants, 
289 ; transmission, 292 ; vaccination, 293 ; see Ba- 
cillus dysenterioe. 

Eclampsia, relation of syncytiotoxin to 171 

Eczema, relation of staphylococcus to 376, 377 

Eel serum, antitoxin for 90 

Ehrlich's partial saturation method 80, 209 

Ehrlich's "side-chain" theory. See "Side-chain" the- 
ory of Ehrlich. 

Emboli, bacterial 4 

Endocarditis. 

Colon bacillus in, 302 ; gonorrheal, 386 ; pneumococcus 
in, 344, 348 : staphylococcus in, 359, 377 ; strepto- 
coccus in. 354, 358. 359. 
Encephalitis, in epidemic cerebrospinal meningitis.... 391 

Endocomplement 159, 266 

Endotheliotoxin, of venom 265 

Endotoxins 330 

Anthrax bacillus, 330 ; Bacillus pyocyaneus, 260, 261 ; 
bacteria containing, 226, 231 ; cholera vibrio, 309 ; 
diseases associated with, 269 ; dysentery bacillus. 
291 ; failure of bactericidal serums to neutralize, 
227 ; glanders bacillus. 453 ; of gonococcus, 385 ; 
leprosy bacillus. 450 ; liberation of, by bacteriolytic 
serums, 136, 228; meningococcus, 390; paratyphoid 
bacillus, 287 ; plague bacillus, 318 ; pneumococcus, 
339 ; staphylococcus, 262, 373 ; streptococcus, 262. 
353 ; tubercle bacillus, 411 ; typhoid bacillus, 271. 
Enteritis. 

Amcha coli in; see Amebic dysentery; Balantidium 
coli in, 505 ; Cercomanas intestinalis in, 506 ; colon 
bacillus in, 303 ; pneumococcus in, 348, 349 ; staph- 
ylococcus in, 377 ; streptococcus in. 354, 355, 357 ; 
Trichomonas intestinalis in, 507. 

Enzymes, bacteriolytic, relation to immunity 61, 62 

Enzymes, intracellular 176 

Epilepsv. cytotoxin in 174 

Epithelioma contagiosum of fowls 11 

Epitoxoids 81 

Erysipelas 355 

Effect on tumors, 362 ; experimental production of, by 
streptococcus. 355 ; in course of tuberculosis, 356 ; 
recurrence of, 56 : staphylococcus in, 355 ; strepto- 
cocci in, 350, 354. 

Etiology, infectious 7 

Etiology, unknown 10, 510 

Exhaustion, toxin of 174 

Farcin flu brruf 463 



584 INDEX. 

PAGE. 

Farcy, see Glanders 10 

Fermentation, early studies on . 27 

Fibrin, mechanical value of in inflammation. 45 

Fixator, synonyms for . 148 

See Amboceptors. 

Filaria perstans 487 

Filaria sanguinis hominis 4 

Fish, B, enteritidis in poisonous 297 

Fish poisons, antitoxins for 90 

Fleas, in the transmission of plague 320, 321 

Flies, as carriers of typhoid fever 272 

Fomites 3, 532, 539 

Food-substances. 

Fixation of, by amboceptors, 208 ; manner of union 
with cells, 197 ; non-formation of antibodies for, 199. 

Foot and mouth disease 11, 12 

Fowls, epithelioma contagiosum of 11 

"Gambian Fever" ; see Trypanosomatic Fever. 
Gastric juice. 

Protective role of, 39, 313. 329. 

Gelatinase 371 

German measles (Rotheln) 562 

Glanders (Farcy) 10, 36, 452-458 

Agglutination reaction, 458 ; animals, susceptibility of, 
452 ; bacilli, distribution of, in the body, 454 ; 
connective tissue development in, 456 ; diagnosis, 
bacteriologic, 457 ; healing processes in, 456 ; im- 
munity, 456 ; infection atria, 454, 455 ; mallein 
in diagnosis of, 457 ; organs involved, 456 ; pha- 
gocytosis, 456; serum therapy, 457 ; tissue reactions, 
455 ; see Bacillus mallei. 
Glossina palpalis in transmission of sleeping sickness . . 488 
Gonococcus ; see Micrococcus gonorrheas. 

Gonorrhea 10, 56, 384-388 

Acute and chronic, 387, 388 ; complications of, 386, 
387 ; immunity, 56, 387, 388 ; ophthalmia in, 386 ; 
phagocytosis, 385, 389 ; reinfection, 387, 388 ; su- 
perinfection, 388 ; susceptibility of different tissues 
to, 386 ; urethral changes, 387 ; see Micrococcus 
gonorrheas. 

Gonotoxin 386 

Grass bacilli 444 

Gregarina lindemanni; see Sarcosporidia. 

Group agglutination 110. 113, 284, 287, 298, 348, 369 

Gruber-Widal reaction ; see Agglutination. 

Hairs, phagocytosis of pigment by chromophages .... 179 

Halteridium. 

Impregnation of parasite, 468 ; in malaria of birds, 483. 

Haptophores 79, 197, 199, 207 

Haptophorous groups ; see Haptophores. 

Hauptagglutinins HI 

Hay fever 262, 263 

Antitoxin (pollantin). 90, 263; pollen as cause of, 
262 ; toxin of, 262. 
Hanging-drop preparation 98 



IXDEX. 585 

PAGE. 

Hemagglutinins. 

Of plants, 103 ; of serums, 104 ; of venom, 265. 

Hemoglobinuric fever, in malaria 477 

Hemolysins. 

Animal, 264, 268 ; bacterial, 202 ; cobra lecitbid, 160, 
266, 571 ; colloids as, 160 ; experimental value of, 141 ; 
from organ extracts, 180 ; immune, in serums, 62, 
141 ; intraleucocytic, 180 ; normal, in serums, 54 ; 
pyocyanolysin, 260 ; serum hemolysins, structure of, 
141 ; staphylococcus, see Staphylolysin ; streptococ- 
cus, see Streptocolysin ; tetanolysin, 249 ; venom, 
of, 265. 
Hemolysis, see Hemolysins. 
Hemolytic experiments. 

Technic of, 141 ; value of, in study of immunity, 142 

Hemorrhagic septicemia group of bacteria 316 

Hemorrhagin 159, 265 

Hemotoxins 67 

Hepatotoxins 171 

Heterologous serum 94 

Homologous serum 94 

"Horror autotoxicus" 17\ 

Horsepox 554 

Hydrophobia 10, 510-521 

Animals, in, 513, 514 : antiserum, properties of, 421 ; 
diagnosis, in dogs. 515, 516 ; extension through 
nerves, 517 ; fixed virus of, 513 ; immunity, charac- 
ter of, 521 ; immunization, mixed, 521 ; incubation 
period, 514, 515, 517, 518 ; micro-organisms found 
in, 510 : Negri bodies, 510, 511 ; Pasteur treatment, 
518, 521 ; prophylaxis of, 517, 521 ; specific ( ?) le- 
sions, 516 : street virus of, 512 ; transmission of, 
514: toxin, question of. 511; vaccination, 29, 30, 
519 ; vaccine, preparation of, 51S, 519 ; virulence 
for man, 513, 517, 520 ; virulence, increase and de- 
crease of, by passage, 513 ; virus, attenuation of, 
58. 219. 511, 518-520; virus de rue. 513; virus, dis- 
tribution and excretion of, 513 : virus, filterability 
of. 12. 511; virus fixe, 513, 518; virus, resistance 
of, 512. 

Ichthyosismus 256 

Ichthyotoxin 268 

Immunity. 

Absolute. 21 : acquired, 18, 56-64 ; active, 21, 56. 59 ; 
antibacterial, 19, 47, 48, 49, 211 ; antitoxic, 19, 49, 
50, 210; definition of, 17; in families, 18; leuco- 
cytes, relation to ; see Phagocytosis ; natural, 18, 
35-55 ; early theories of, 24 ; passive, 21, 60 ; rela- 
tive, 21 ; theories of, 30-34 ; types of, 22 ; see An- 
titoxins, Bacteriolysins, Phagocytosis and the indi- 
vidual diseases. 
Immunization. 

Active, as curative measure, 220 ; active, for prophyl- 
axis. 232; classification of methods, 218; choice of 
animals for, 229 ; mixed, 220, 234 ; passive, as cura- 



586 INDEX. 

PAGE. 

tive measure, 220 ; passive, in prophylaxis, 220 ; 
with tissue cells, 164 ; with toxins, 33. 
Impetigo contagiosa. 

Staphylococcus in, 354 ; streptococcus in, 357. 

Incubation period 210 

Infection. 

"Air borne," 3 ; atrium of, 3, 35, 39 ; contact, by, *3 ; 
mixed, 11, 14, 15, 113 ; see individual diseases ; 
"water borne," 3 ; infectious agents, classification 
of, 6. 

Infectiousness and contagiousness 2 

Infestation 2 

Inflammation. 

Antagonism of, to infections, 46 ; chemotaxis, 43 ; 
connective tissue, inflammatory rQle of, 41, 46 ; 
fibrin, influence of, 45 ; injurious effects of, 41, 42 ; 
leucocytes in, 43-45 ; nature of, 41 ; organization in, 
45 ; phagocytosis in, 43-45 ; plasma, influence of, 
45 ; relation of, to virulence of bacteria, 42, 43 ; 
role of, in immunity and resistance, 41 ; variations 
in intensity, 42-44. 

Influenza 10, 393-399 

Conjunctivitis in, 37, 397 ; chronic, 397 ; contagiousness 
' of, 393 ; epidemics of, 393 ; immunity, 398 ; infec- 
tion atrium, 397 ; intestinal, 396 ; intoxication, 
396 ; meningitis in, 396, 397 ; mixed and secondary 
infections in, 397 ; otitis media in, 396, 397 ; peri- 
tonitis in, 396, 397 ; phagocytosis in, 396 ; pneu- 
monia during, 344, 396 ; prophylaxis, 398 ; recur- 
rence of, 56, 398 ; susceptibility, 398 ; transmission 
of, 397 ; tuberculosis during, 397 ; see Bacillus in- 
flcn&ce. 

Injuries, mechanical and toxic, by bacteria 4 

"Intestinal group" of bacteria 270 

Intoxications, infectious 15 

Isoagglutinins 104 

Isoprecipitins 121 

Lactoserum 120, 125 

Lamolia intestinalis 508 

"Leistungskern" 86, 195 

Lecithin as endocomplement 159 

"Leprolin" 450 

Leprosy 10, 445-452 

Animals, insusceptibility of, to, 447 ; contagiousness 
of, 446 ; distribution of bacilli in the body. 449 : 
extension and occurrence of, 445 ; fish, relation of 
to, 448 ; infection atria, 448 ; intercurrent infections, 
450 ; phagocytosis in, 449, 451 ; potassium iodid in 
treatment of, 450 ; prophylaxis, 451 ; protective 
factors in, 451 ; serum therapy of, 452 ; spontaneous 
disappearance of, 450 ; susceptibility to, 451 ; trans- 
mission of, 448 ; tubercular, 450 ; see Bacillus leprw. 

Leptothrix, infections by 463 

Leptothrix oaccalis 463 

Leptothrix vaginalis 463 



IXDEX. 587 

PAGE. 

Leucocidin 67, 202, 373, 3S0, 382 

Antitoxin for, 372 ; influence on phagocytosis, 372. 

Leucocytes. 

Absorption of toxins by, 191 ; complement in, 154 ; for- 
mation of precipitins by, 121 ; immunity, relation 
to, 176-194 ; in inflammations, 43 ; phagocytic prop- 
erties of, 43, 44, 45 ; see also individual diseases ; 
see Phagocytosis. 

Leucocytic exudates, bactericidal action of 37S, 379 

"Loop," standard 101 

Leucotoxic serum 167, 168 

Leucotoxin ; see Leucotoxic Serum. 

"Lumpy jaw" ; see Actinomycosis. 

Lupus, influence of streptococcus on 362 

Lymphangitis, streptococcus in 354-356 

Lymphatotoxin ; see Leucotoxic Serum. 

Macrocytase ITS 

Macroparasites 6 

Macrophages 44, 168, 178, 184 

Madura foot ; see Mycetoma. 

Mai de cederas ; see Trypanosomiasis in animals. 

Malaria 468-483 

JEstivo-autumnal, 469 ; a?stivo-autumnal, parasite of ; 
see Plasmodium prcecox ; anemia in, 474 ; "black- 
water fever" in, 477 : cachexia in, 476 ; cerebral 
symptoms, 477 ; epidemiology of, 477 ; etiology 
of, 468 ; fever, relation of to developmental cycles 
of parasites, 474 ; hemoglobinuric fever in, 477 ; 
immunity, acquired, 481, 482 ; incubation period, 
473; intestinal symptoms. 477; melanemia in, -174: 
methylene blue in, 474 ; mixed infections, 476 ; 
mosquitoes, transmission by, 468 ; neuralgia in, 
476 ; parasites, localization of, 477 ; prophylaxis 
of, 480, 481 ; quartan, 469 ; quartan, parasite of ; 
see Plasmodium malariw; quinin in prophylaxis and 
treatment of, 476, 477. 481 ; quotidian, 475 ; para- 
sites, localization of, 473, 474, 477 ; relation of 
clinical symptoms to developmental cycles of para- 
sites, 473 ; susceptibility to, 481 ; tertian, 469 ; 
tertian, parasite of; see Plasmodium vivax ; toxins. 
474. 475 ; transmission ; see Anopheles ; see Plas- 
modium of malaria. 

Malaria of birds, halteridium in : proteosoma in 483 

Malignant pustule; see "Anthrax." 

Mallein 220, 454. 457 

Malta Fever 333-335 

Accidental infections, 335 ; agglutination reaction in, 
334 ; difference from typhoid fever, 334 ; distribu- 
tion of bacillus in body, 334. 335 ; immunity, 335 ; 
occurrence, 333 ; serum, properties of. 334 ; serum 
therapy, 335; transmission, 335; see Bacillus meli- 
t< nsU. 

Measles 559-502 

Complications and sequela*. 560; contagiousness of. 
559 ; immunity and susceptibility, 561 : leprosy, 
influence on. 450; leucocytes In, 561: Micrococcus 



588 



INDEX. 



PAGE. 

catarrhalis in, 384 ; micro-organisms in, 559 ; 
prophylaxis, 560 ; racial immunization, 561 ; resist- 
ance of virus, 560 ; recurrences, 561 ; serum therapy, 
561 ; virus, distribution of, 559, 560. 

Meat poisoning. 

Bacillus botulinus in, 256 ; Bacillus enteritidis in, 
294-298 ; Bacillus paratyphosus in, 285 ; relation of 
ptomaines to, 295. 

Mechanical and toxic injuries 4 

Mediterranean fever, see Malta fever. 

Meningitis. 

B. pneumonia in, 402 ; colon bacillus in, 302 ; in in- 
fluenza, 396 ; micro-organisms causing, 388, 189 ; 
pneumococcus in, 344, 348, 349 ; secondary, 356, 
357 ; streptococcus in, 354, 356, 357 358 ; tubercu- 
lous, 420. 

Meningitis, epidemic cerebrospinal 388-393 

Agglutination test, 393 : cerebrospinal character of, 
391 ; complications, 391 ; contagiousness of, 392 ; 
immunity, acquired, 392 ; lumbar puncture for diag- 
nosis, 391 ; metastatic infections, 391 : mixed and 
secondary infections in, 391 ; prophylaxis of, 392 ; 
secondary to rhinitis, 390 ; serum, properties of, 
393 ; susceptibility to, 392 ; transmission of, 392 ; 
see Micrococcus meningitidis. 

Meningococcus ; see Micrococcus meningitidis. 

Metchnikoff s theory ; see Phagocytosis. 

Methylene blue, effect of, on malarial parasites 474 

Microbic specificity 27 

Micrococcus catarrhalis 383. 384 

Animals, susceptibility of, to, 384 ; bronchitis, in, 384, 
391 ; measles, in, 384 ; occurrence in respiratory 
passages, 383 ; occurrence under normal conditions, 
384 ; pneumonia, in, 337, 344, 384, 392 ; resemblance 
to meningococcus, 392 ; scarlet fever, in, 384 ; 
whooping-cough, in, 383. 

Micrococcus gonorrhece (gonococcus) 383 

Antiserum for, 388 ; cultivation of, 384, 385 ; discovery 
of, 384 ; endotoxin of, 385 ; gonotoxin, 386 ; im- 
munization with, 388 ; infections with, 384, 388 ; 
morphology, 384 ; phagocytosis of, 385, 387 ; re- 
sistance of, 385 ; toxin, soluble, 388 ; see Gonorrhea. 

Micrococcus hcmatodes 374 

Micrococcus melitensis, see Bacillus melitensis. 

Micrococcus meningitidis (Diplococcus intracellularis 

meningitidis, or the meningococcus) 10, 3S8-393 

Agglutination of, 393 ; animals, susceptibility of, 390 ; 
antiserum, properties of, 392, 393 ; bronchitis, in. 
391 ; conjunctivitis, in, 391 ; cultivation, 390 ; dis- 
covery, 389 ; endotoxin, 390 ; excretion of, 392 ; im- 
munization with, 393 ; morphology, 390 ; pneumonia, 
in, 391 ; resemblance to gonococcus, 389 ; resem- 
blance to Micrococcus catarrhalis, 392 ; resistance, 
390 ; rhinitis, in, 391 ; virulence, 390 ; see Menin- 
gitis, epidemic cerebrospinal. 

Microbic specificity 27 

Microcytase 178-189 



IXDEX. 589 

PAGE. 

Micro-organisms. 

Early belief in, 25 ; recognition of, 26 ; ultrarni- 
croscopic. 6. 

Microparasites 6 

Microphages 44, 178, 184, 190 

Microsporon septicum (Klebs) 349 

Milk bacilli 444 

Mitagglutinin Ill 

"Honadinin" of Klebs 359 

Mucor 467 

Mumps (epidemic parotitis) 566 

Mycetoma 462 

Nagana ; see Trypanosomiasis in animals 493 

Natural immunity ; see Immunity. 

"Negative phase" following vaccinations 233 

Negri bodies ; see Hydrophobia. 

Nephrotoxin 169, 170 

Neuronophages 179 

Neurotoxin of serums 171 

Neurotoxin of venom 67, 265 

Oidia 6, 10 

Oidiomycosis 463-467 

In animals. 467 : cutaneous, 463 : infection atria, 
465 • organisms of. 464 ; resemblance to tubercu- 
losis, 465 ; systemic, 464 ; thrush, 466. 

Oidium 464 

Agglutination, immunization and phagocytosis, 467. 

Oidium albicans 466 

Oidium coccidioides 465 

Old age, MetchinkofTs theory of 168 

Ophthalmia. 

Cytotoxins in, 173 : gonorrheal, 3S6. 

Opsonic index X. . . *-. . ..^882 

Opsonins 61, 193, 227; 369 

Action of salts on, 194; in acquired immunity, 6; see 
Phagocytosis in different diseases. ' 

Opsonoid 194 

Otitis media. 

B. influenzae in. 396. 397 : pneumococcus in, 348 ; 
staphylococcus in. 377 ; streptococcus in, 358 ; tuber- 
culous, 420. 

Oxvtuberculin 413 

Ozena 402 

Pancreatic juice, action on toxins 40 

Pancreotoxin 1 73 

"Paracolon'* bacilli 285 

Parasites, pathogenic 1, 6 

Parasitism 1 

Parotitis, epidemic; see Mumps. 
Passive immunity ; sec Immunity. 

Paratyphoid fever 284-288 

Agglutination reaction in, 287, 288 : blood cultures in, 
288: characteristics of the disease. 286: endotoxin 
of bacilli. 287 ; epidemiology of. 285 : as meat pois- 
oning, 285 : occurrence of bacilli in the body. 286 ; 
properties of serum, 287: prophylaxis. 287: trans- 
mission. -- iee Baoillua pardtyphoaua. 
Passage 58 



590 INDEX. 

PAGE. 

Pasteur treatment ; see Hydrophobia. 

Pathogenesis 4, 5 

Peripneumonia of cattle 11, 12 

Periostitis albuminosa 377 

Periostitis, staphylococcus in 377 

Teritonitis. 

Colon bacillus in, 303 ; by influenza bacillus, 396, 
397 ; pneumococcus in, 348, 349 ; staphylococcus 
in. 377 ; streptococcus in, 354, 357 ; tuberculous, 420. 
Pertussis ; see Whooping-cough. 

Pfeiffer's phenomenon 96, 131, 132 

In identifying the vibrio of cholera, 305 ; role 6f leu- 
cocytes in, 183. 
Phagocytic (MetchDikoff's) theory of immunity. ... 176, 194 
Comparison of, with the side-chain theory of Ehr- 
lich, 212, 215 ; see Phagocytosis. 

Phagocytosis 31, 44, 176-194, 215 

In active immunity, 59, 60, 192, 193; chemotaxis in, 
177, 185 ; fixators, influence of, 190 ; in inflamma- 
tions. 43 ; intestinal, 41, 177 ; intravascular, 188 ; 
leucocidin, influence of, 372 ; in nutrition, 172 ; op- 
sonins,, role of, 193 ; in passive immunity, 60, 192, 
193 ; relation of to virulence of bacteria, 184, 187 ; 
in resorption, 178 ; serum, influence of, 187, 193 ; 
in vitro, 49. 193 : see under the individual micro- 
organisms and diseases ; see Opsonins. 

Phagolysis 181, 182, 188, 190 

Phallin 264 

Phrynolysin 268 

Phytoprecipitins 120 

Plagiomonas urinaria . . 508 

Plague 10, 315-327 

Agglutination reaction, 326, 327 : animals, suscepti- 
bility of, 319 ; contagiousness, 322 ; diagnosis, bac- 
teriologic, 323 ; dissemination of bacillus by urine, 
feces, sputum, 322 ; epidemiology, 320, 323 ; foci of, 
320 ; immunity, 56, 60, 324, 325 ; infection atria, 

322 ; mixed immunization in, 234, 324 ; mixed in- 
fection in. 323 ; occurrence, 315 ; houses. 321 ; 
prophylaxis, 323 ; in rats, 320 ; serum therapy, 325, 
326 : transmission by fleas, 320, 321 ; transmission 
from rat to man, 320, 321 ; vaccination, 58, 218, 

323 ; vaccines, 323, 324 ; see Bacillus pestis. 

Plasmin of Buchner 68, 219 

Plasmodia of malaria 4, 10, 468 

Anopheles mosquito as host of, 9, 469 ; asexual cycle. 
469 ; development in anopheles, 470 ; development 
in man, 469 ; discovery of, 468 ; flagella of, 468 ; 
macrogamete, 470 ; merozoites, 470 ; methylene blue, 
effect of, 474 ; microgamete, 471 ; microgametocyte, 
470 ; oocyst, 471 ; ookinet, 471 ; schizogony, 470 ; 
sexual cycle, 470 : species of, 469 ; spermatozoites, 
468 ;. sporocyte, 470 ; sporogony, 471 ; sporozoites, 
471 ; see Malaria. 

Plasmodium malaria 469 

Relation to clinical symptoms. 473 : sexual and asex- 
ual cycles of, 472 : virulence, 474. 

Plasmodium prwcox 469 



INDEX. 591 

PAGE. 

Relation to clinical symptoms, 473 ; sexual and asexual 
cycles of, 472 ; virulence, 473. 

Plasmodium vivax 469 

Asexual cycle of 469, 470 ; relation of to clinical 
symptoms, 473 ; sexual cycle of, 470, 471 ; virulence 474 
Pneumococcus ; see Diplococcus pneumonia. 

Pneumonia 336-348 

Agglutination reaction, 347 ; B. pneumoniae in, 402 
bacteria causing, 336, 337 ; causes, predisposing, 
343 ; complications, 343, 344. 348 ; contagiousness, 
342 : immunity and susceptibility, 56, 345 ; infection 
atrium and method of infection, 340 : influenza bacil- 
lus in, 396 ; leucocytes, 345 ; metastatic infections, 
348 ; phagocytosis, 345 ; meningococcus in, 391 ; 
Micrococcus catarrhal is in, 384, 392 ; mixed infec- 
tions in, 344 ; polyvalent serum for, 347 ; prophy- 
laxis, 344 ; recurrences, 345 ; Roemer's serum, 347 ; 
serum properties, 345 ; serum therapy, 346. 347 : 
staphylococcus in, 377 ; streptococcus in, 354, 355. 
356: vaccination, 345; see Diplococcus pneumonia 
and other bacteria enumerated on page 336. 

Pneumotoxin 339 

Pollantin 263 

Pollens. 

As cause of hay fever, 262 ; antitoxin for, 263. 

Polyceptors 155 

Polyvalent serums. 

For pneumococcus. 347 ; for staphylococcus. 3S3 ; 
for streptococcus, 232, 366. 

"Positive phase" following vaccination 233 

Postmortem invasion 302 

Precipitate 120, 124, 125 

Precipitation reaction 106, 119 

Agglutination, relation to, 117 : as clinical reaction, 
119: with colloids and electrolytes, 128, 129; 
forensic use of. 63. 125 : precipitation, group reac- 
tion. 125. 126: meats, differentiation of, 127; physi- 
cal chemistry in the study of, 129 ; specific inhibi- 
tion. 122 : technic, 126 ; use of in studying reactions 
of immunity, 206. 

Precipitins 110-129 

Antiprecipitins, 123; autoprecipitina. 121; bacterial, 
63. 119. 233. 314; formation of, 121: isopreeipitins. 
121: [actoserum, 120: phytoprecipitins. 120; re- 
sistance to ferments, heat, etc.. 122; serum precipi- 
tins, immune. 63: serum precipitins, normal. 55; 
structure of. 122 ; zobprecipitins, 120. 

F'recipitoeens 120 

Preclpltolda 122 

Pregnancy, serum diagnosis 172 

Preparator 148 

Proagglutinoids 109 

Prophylactic Injections, classification of methods 218 

Protective inoculation: see Vaccination. 

Proteins 220 

Proteosoma in malaria of birds 483 

Prototoxln 83, 20b 

Protoxolds 82. 209 



592 



INDEX. 



PAGE. 

Protozoa, infections with 468, 509 

Pseudodiphtheria bacilli 243, 244, 425 

Pseudoinfluenza bacilli 394 

Pseudotuberculosis of animals 444 

Ptomains in meat 295 

Pyocyanase 61, 260 

Pyocyanin 260 

Pyocyanolysin 260 

Pyroplasma bovis; see Texas fever. 
Pyroplasrna hominis; see Spotted fever 
Pyroplasmosis ; see Spotted fever and Texas fever. 
Rabies ; see Hydrophobia. 

Radium, effect on venom 267 

Rats in epidemics of plague 320, 321 

Rattlesnake venom. 

Antiserum for, 267 ; immunization with, 219. 

Ray fungus ; see' Actinomyces 320, 321 

Receptors. 

Bacterial, 152 : function of, 52, 87, 88 : immunity, re- 
lation to, 199; loss of, as cause of immunity, 240; 
multiplicity of, 86, 208 ; new formation of, 199, 205, 
207 ; nutrition, relation to, 195 ; of first order, 89, 
200. 207 ; of second order, 114 203, 207, 209 ; of 
the third order, 150, 203, 207 ; synonym for side 
chain, 197 ; tetanophile receptors of nervous tissue, 
252 ; types of, 207 ; see different antibodies. 

Relapsing fever 10. 403-406 

Agglutination test, 406 ; immunity and susceptibility, 
404, 406 ; organism of ; see Spiroclieta ober- 
meieri ; phagocytosis in, 405 ; prophylaxis, 404 ; 
serum properties, 405, 406 ; serum therapy, 406 ; 
transmission of by bedbugs, 404. 
Resistance, natural ; see Immunity, natural. 
Resorption. 

Of foreign cells, 179 ; of native cells, 178. 

Rheumatic fever 359, 360 

"Agonal invasions in, 359 ; antistreptococcus serum in, 
368 ; bacillus of Achalme in, 359 ; diplococcus 
(streptococcus) in, 360; experimental, 359. 360; 
micro-organisms found in lesions, 359 ; staphylococ- 
cus in, 359 ; streptococcus in, 354, 359. 360 : 
Zymotosis translucens, 359. 
Rhinitis. 

Meningococcus in, 391 ; pneumococcus in, 348 ; pri- 
mary to meningitis, 390 ; staphylococcus in, 377 ; 
Rhinitis fibrinosa, 237. 

Rhinoscleroma 402 

Ricin 6. 264 

Antiricin, 63 : Ehrlich's use of in studying nature of 
antitoxic action, 201, 202 ; hemagglutinin in, 104. 

Robin 264 

Rotheln, see German measles. 

Saccharomycosis hominis 464 

Salamander poison, antitoxin for 90 

Saprophytes 1 

In tetanus 248 

Sarcocystis hominis; see Sarcosporidia. 



INDEX. 593 

PAGE. 

Sarcosporidia. 

Morphology, occurrence and proliferation, 504, 305 ; 
Sarcocystis hominis, 505. 

Scarlatina ; see Scarlet fever. 

Scarlet fever (scarlatina) 556-559 

Agglutination of streptococci by serum, 369, 370 ; con- 
tagiousness, 557 ; Cyclaster scarlatinalis in, 556 ; 
Diplococcus scarlatinas, 11 ; leucocytes in, 558 ; 
Micrococcus catarrhalis, 384 ; micro-organisms in, 
557 ; prophylaxis, 557 ; protozoa in, 10, 556 ; 
resistance of virus, 557 ; serum therapy, 558, 559 ; 
streptococcus in. 14, 15, 186, 354, 355, 358, 361, 
556 ; Streptococcus scarlatina?, 361 ; immunity and 
susceptibility, 56, 558; serum therapy (antistrep- 
tococcus), 366, 368, 558; transmission, 557. 

Scorpion, toxin and antitoxin 90, 268 

Sensitization 145 

Serpent ulcer. 

Pneumococcus in, 348, 349 ; treatment with antipneu- 
mococcus serum (Roemer), 349. 

Serums, purity of 76, 221 

Serum therapy, principles of 218-234 

Antitoxins, 221, 226; bactericidal serums, 226, 232; 
classification of methods, 218 ; curative injections, 
220, 223, 227 ; prophylactic injections. 218, 226, 
227 ; see also under the different diseases. 

Sheep-pox ; see Clavelee. 

Side-chain theory of Ehrlich 195-217 

Amboceptor formation, 150 ; agglutinin formation, 
114 ; antitoxin formation, 86, 89 ; applied to cell 
nutrition, 195 ; as applied to immunity, 199 ; chem- 
ical processes, 78, 200, 205, 208 ; complements, 153, 
210 ; essential tenets of, 200 ; haptophores, 197 ; 
"Leistuvr/skern/' 195 ; Metchnikoff's phagocytic the- 
ory, comparison with, 212, 217 ; precipitin forma- 
tion, 121 ; receptor proliferation, 205 ; receptors, 
types of, 207 ; side chains, 195. 

Sleeping sickness 486-490 

Anatomic lesions of, 489 ; bacteria in, 487 ; occur- 
rence. 486, 487 ; symptoms of, 488, 489 ; transmis- 
sion of, 488 ; Trypanosomatic fever, relation to, 489, 
490 ; trypanosomes in, 487 ; see Trypanosomiasis. 

Smallpox ! 541-555 

Bacteria in. 542, 548 ; conversion into vaccinia, 541, 
542 ; cyclic nature of symptoms, 547 ; Cytoryctes 
variola? s. vaccinia?, 543 ; dissemination of virus, 
546; etiology. 542; fetal. 548; immunity and sus- 
ceptibility, 56, 554 ; incubation period, 547 ; infec- 
tion atrium, 546; inoculation into calves, 541; 
Jennerization, 549 ; leucocytes in, 554 ; mixed (sec- 
ondary) infections, 15, 548 ; nonfiltrability of virus, 
542 ; prophylaxis, 548 ; protozoon-like bodies in, 
11, 542 ; relation to vaccinia. 57, 541 ; revaccina- 
tion, 552, 553 ; serum properties, 554 ; transmis- 
sion, 546 : vaccination, 548 ; vaccine, contamina- 
tions of, 551, 552 ; vaccine, durability of, 551 ; viru- 
lence, variations in, 547 ; virus, distribution In the 
body, 547. 



594 INDEX. 

PAGE. 

Smallpox and vaccinia 541, 555 

Smegma bacilli 443 

Snake bites 264, 268 

Soft cbancre or chancroid 399-401 

In animals, 400 ; bacillus of, 400 ; immunity, 401 ; in- 
dependence, 399 ; infectiousness of, 399 ; phago- 
cytosis, 400, 401. 

Specific infections 9 

Spermophilus columManus as host of Pyroplasma 

hominis . 498 

Spermotoxin 165, 166 

Spider poison, antitoxin for 90 

JSpiroeheta obermeieri 10, 403 

Agglutinins for, 406 ; animals, susceptibility of, 404 ; 
antiserums, properties of, 405 ; distribution in the 
body, 403 ; morphology, 403 ; occurrence in bedbugs, 
404 ; phagocytosis of, 405 ; see Relapsing fever. 

Spirocheta pallida (see syphilis) 525, 526 

"Spotted fever" 497, 498 

Pyroplasma hominis in 497 

Staphylococcus pyogenes, or staphylococcus 370-383 

Agglutination, 92, 382 ; amyloid degeneration, 375 ; 
animals, susceptibility of, 375, 376 ; antiserums, 
properties, 380 ; bactericidal action of leucocytic 
exudates, 378, 379 ; bacteriolysin, 379, 380 ; dis- 
covery, 350 ; endotoxin, 373 ; ferments of, 371 ; 
hemolytic action, 5, 371, 372 ; immunity, 186. 379, 
380 ; leucocidin, 372, 373, 380. 382 ; leucocytes 
in infections, 378. 379 ; leucotactic substance, 375 ; 
mixed infections, 378 ; morphology, 370 ; necrotiz- 
ing substance, 375 : pathogenic powers, 37, 336. 
344, 354, 359, 376, 378, 389 ; opsonins in phagocy- 
tosis of, 382 ; phagocytosis, 378, 379, 380, 382 ; 
pigment formation, 374 ; polvvalent serum. 383 ; 
resistance, 374, 375 ; staphylolysin, 271, 372, 373, 
375, 380 ; symbiosis with Ameba coli, 502 ; symbio- 
sis with B. influenza, 394 ; toxicity of culture 
filtrates, 372, 373 ; toxin, soluble, 375 ; vaccination 
against, 381 ; varieties, 373, 374 ; virulence, 376. 
Staphylolysin ; see Staphylococcus. 

Stegomyia fasciata and its relation to yellow fever 531 

Streptococci in scarlet fever 14, 354, 355, 358, 361 

Streptococcus brevis 350 

Streptococcus erysipelatis 350 

Streptococcus longus 350 

Streptococcus mucosus capsulaius 351 

Streptococcus pyogenes 349-370 

Agglutination, 92, 369, 370 ; animals, susceptibility of, 
352 ; antagonism for B. anthracis, 329, 362 ; for B. 
tuberculosis, 356 ; antistreptococcus serum, proper- 
ties of, 362, 368 ; antistreptocolysin, 353 ; bacterio- 
tropic substances, 369 ; Coley's mixture, 362 ; cul- 
tivation, 351 ; in diphtheria, 238, 358 ; discovery, 
350 ; endotoxin, 353 ; erysipelas, 350, 354, 355 ; 
immunity, 186, 363, 364, 365 ; infection atria, 358 ; 
infections, miscellaneous, 354, 362 ; in influenza, 
397 ; leucocytes and leucocytosis, 363. 364 : lupus, 
influence on, 262 ; in meningitis. 354, 389 ; in 
milk, 357 ; morphology, 350 ; opsonins, 369 ; pha- 



IXDEX. 595 

PAGE. 

gocytosis. 363, 364 : in pneumonia, 336. 344, 354, 
355, 356 : resemblance to pneumococcus, 338 ; re- 
sistance, 351, 352 ; in rheumatic fever, 354, 359 ; 
in scarlet fever, 14, 354, 355, 358, 366 ; serum ther- 
apy, 367-369 ; serums, univalent and polyvalent, 
365 ; streptocolysin, 353, 354 ; symbiosis with 
B. influenza;, 394 ; tissue reactions, 42 ; toxic prop- 
erties, 353. 354, 362 ; toxin for erythrocytes ; see 
Streptocolysin ; toxin for leucocytes, 354 ; in tuber- 
culosis. 355, 356, 424, 425 ; tumors, influence on, 
362 ; in typhoid fever, 275 ; unity, question of, 365 ; 
varieties, 350 ; virulence, 352. 

Streptococcus scarlatina; 361 

Streptocolysin 353, 354 

Streptothrix, infections with 463 

Streptothrix madurce 462 

Substance sensibilisatrice 148, 217 

Summer diarrheas ; see Dysentery, acute epidemic. 

Surra ; see Trypanosomiasis in animals 494 

Susceptibility 18, 53, 54 

See the individual diseases. 
Symptomatic anthrax. 

Antitoxin, 90 ; vaccination against, 219. 

Syncytiolysin 171 

Svnonyms 217 

Syntoxoids 83, 209 

Syphilis 10, 522-529 

Animals, non-susceptibility of, 522 ; bacillus of De 
Lisle and Julien, 522 ; bacillus of Joseph and Pior- 
kowski, 522 ; bacillus of Lustgarten, 522 ; Colle"s 
law, 528 ; immunity and susceptibility, 54, 527 ; 
inheritance, 527 ; micro-organisms found in, 522 ; 
monkeys, transmission to, 12, 522 ; reinfection, 
527 ; Spirocheta pallida in, 525 : transmission, 
526 ; virulence, variations in, 527 ; virus, distribu- 
tion of, 526 ; virus, non-fllterability of, 526. 

Tetanolysin 249, 250 

Antitetanolysin, 223 ; neutralization by cholesterin, 91. 

Tetanospasmin 249, 250 

Tetanus 10, 244-256 

Agglutination reaction, 256 ; animals, susceptibility 
of, 51 ; cerebral, 251 ; dirt and necrotic tissue, in- 
fluence of, 247 ; dolorosa, 251 ; excretion of toxin, 
250 ; Fourth of July, 248, 252 : "head tetanus," 
251 ; in horses, 252 ; immunity and susceptibility, 
18. 60, 185, 249, 251 ; "idiopathic," 248 ; incuba- 
tion period, 240; leucocytes, in absorption of toxin, 
250 ; local, 251 ; lumbar puncture, 255 ; mixed infec- 
tions, 14, 248, 249 ; nervous tissue, in fixation and 
transport of toxin, 250 ; non-contagiousness of, 3 ; 
occurrence of bacillus in the body, 249 ; occurrence 
of toxin in the body, 250 ; pathogenesis, 250, 251 ; 
phagocytosis in, 185, 248 ; puerperal, 252 ; rheumat- 
ic us, 248 ; seasons in relation to prevalence, 248 ; 
serum therapy and prophylaxis, 224, 253-255 ; 
toxin (see B. tetani, toxin of) ; treatment of 
wounds, L'."L' : Wassermann's experiment, 250 ; 
wounds favoring development of, -17: s.-e Bacillus 
tetani. 



596 TNDEX. 

PAGE. 

Texas fever 499 

Thrush 466 

Organisms of, 466 ; susceptibility to, 467 ; systemic 
infections, 466. 

Thyrotoxin 173 

"Tick fever" ; see "Spotted fever." 

Timothy bacillus 444 

Toxins. 

Animal, 6, 264-268; attenuation of, 70; bac- 
terial, 6, 235 ; see individual bacteria ; chem- 
otaxis, influence on, 185, 354, 372 ; crotin, 
264 ; degenerative changes in, 80, 209 ; dis- 
covery of, 33 ; effects of, 4, 5 ; endotoxins, 6, 
20, 68 ; see individual bacteria ; gastric juice, de- 
structive action, 39 ; haptophores of, 79, 209 ; see 
side-chain theory ; immunization with, 69, 70, 220 ; 
incubation period of, 65, 251 ; intracellular ; see 
Endotoxins ; leucocidin, 372 ; leucocytes in absorp- 
tion of, 45, 191 ; modifications by age, 85 ; neu- 
tralization by antitoxins, 48, 78, 200 ; pancreatic 
juice, destructive action, 40 ; phallin, 264 ; of 
pollens, 262 ; precipitation of, 66 ; preparation, 66 ; 
properties of, 65, 208 ; as receptors of, second order, 
207 ; ricin, 264 ; robin, 264 ; secondary or adven- 
titious, 67 ; selective action of, 5 ; toxin spectrum, 
81, 209 ; standardization of, 72 ; staphylolysin, 371 ; 
structure, 78 ; toxophores, 80, 209 ; see side-chain 
theory; union with tissue cells, 66, 87, 200, 204, 
224, .222, 252; vegetable, 6, 262-264; see individ- 
ual micro-organisms. 

Toxoids '. 80-83, 209 

Toxon 82, 209, 242 

Toxophorous group, toxophore 80, 207 

Trichomonas intestinalis, morphology and pathogenicity 

of 507, 508 

Trichomonas vaginalis 507 

Trichophyton 467 

Tritotoxin 83, 209 

Trypanosoma 483 

Agglutination of, 485 ; cultivation of, 492, 494 ; 
morphology of, 484 ; multiplication of, 485 ; rosette 
formation by, 485 ; sleeping sickness, 487 ; species 
of, 484, 485, 490 ; trypanosomatic fever, 486. 

Trypanosomatic fever 485, 486 

Sleeping sickness, relation to, 489, 490 ; symptoms 
of, 486 ; trypanosomes in, 486. 

Trypanosomiasis 483-497 

Agglutination reactions, 497 ; immunity and suscep- 
tibility, 495 ; in man, 485-490 ; parasites, occurrence 
of in the blood, 491 ; serum therapy of, 496 ; 
'trypanroth" in treatment of, 496 ; vaccination 
• in, 496 ; see Sleeping sickness and Trypanosomatic 
fever. 

Trypanosomiasis in animals 490-495 

Dourine, 495 ; horses, cattle and mules, 493-495 ; 
mal de cederas, 495 ; nagana, 493 ; in rats, 491 ; 
surra, 494 ; symptomatology, 491. 



IXDEX. 597 

PAGE. 

"Trypanroth" in treatment of trypanosomiasis 496 

Tsetse flies, in transmission of trypanosomiasis ; see 
Trypanosomiasis. 

Tuberculin of Koch and others 219, 220, 412, 413, 414 

Dangers, errors and limitations in use, 434, 435 ; 
diagnostic use of, 432-436, 442 ; disturbances caused 
by, 433 ; immunization with, 411, 431, 432 ; prepara- 
tion of, 412 ; principles of action, 437 ; .specificity 
of. 434. 435 ; standardization of, 412, 414"; therapy, 
436, 437. 

Tuberculocidin 413 

Tuberculosis 10, 407-443 

Agglutination as an index of immunity to, 
437 ; agglutination reaction, 438. 440 ; amy- 
loid degeneration in, 424 ; "anatomic tubercle," 
419 ; in animals, 427, 441 ; avian, 442 ; bovine, 441 ; 
bovine, relation of, to human, 415-417 ; congenital, 
417 ; disinfection in, 426 : dissemination by means 
of phagocytes, 421 ; "droplet infection," 418 ; 
"dust infection." 418 ; healing, spontaneous, 420 ; 
heredity in, 429 ; immunity and susceptibility, 18, 
19. 61, 427, 430-432, 437; immunization, mixed, 
439 ; infection atria, 418, 420 ; infectiveness of, 
407 ; latent. 418 ; lupus vulgaris, 419 ; metastases 
in, 420 ; miliary, 421 ; mixed infections in, 424 ; 
organs attacked, 419-421 ; phagocytosis, 421, 422 ; 
pneumonia during, 344 ; predisposing factors to, 
42S. 429 : primary and secondary, 421 ; propby- 
laxis. 425, 427 ; pulmonary. 418 : serum therapy, 
425, 438 ; streptococcus in, 355, 356 ; tissue changes 
in, 5. 422-425 ; tuberculin in diagnosis. 432-436 ; 
ulcerative, 419 ; vaccination against, 439. 

Tumors, influence of streptococcus on 362 

Turtle poison, antitoxin for 90 

Typhoid fever 10, 269-284 

Agglutination reaction, 7, 95, 283, 284 ; antibodies, 
origin of, 190; bacillemia. 272, 273; bacilli, distri- 
bution in the body, 273, 274 ; blood cultures for di- 
agnosis, 273. 284 ; "dust" infection, 272 ; epidemi- 
ology of, 271 ; flies as carriers, 272 ; immunity and 
susceptibility, 56, 60, 61. 275 ; infection atrium, 
272 ; leucocytes, 274. 277 ; leucotoxin in experi- 
mental infections, 168 ; mixed immunization, 234, 
282 ; mixed infections in, 275 ; serum properties, 20 
prophylaxis. 278 : serum prophylaxis, 279 ; serum 
therapv, 230, 282 ; therapy, active immunization, 
283 ; therapy of Jez. 283 ; vaccines and vaccina- 
tion, 58, 218, 279, 282 ; see B. typhosus. 

Typhus fever 10, 538-541 

Conditions for development, 538 ; contagiousness, 539 : 
fomites, 539 ; micro-organisms in, 538 ; occurrence, 
538 ; prophylaxis, 539 ; pyroplasma ( ?) in, 538 ; 
serum therapy, 539 ; transmission, 530. 

Ultramicroscopic micro-organisms 12 

litx inaria duodenalis 4 

Undulant fever; see Malta fever. 

Univalent serums 366 

Urease 90 



598 INDEX. 

PAGE. 

Vaccination 28, 57, 218-220, 232-234 

Antibodies produced by, 233 ; duration of resistance 
caused by, 232 ; incubation period, relation to, 
234 ; see Smallpox and Hydrophobia ; opsonins, in- 
crease of, 234 ; "positive" and "negative phases," 
233 ; substances used for, 218-220 ; see the indi- 
vidual diseases. 

Vaccines 218-220, 232-234 

See the individual diseases. 

Vaccinia ; see Smallpox and Vaccinia. 

Varicella ; see Chickenpox. 

Variola inoculata 546, 591 

Variola ; see Smallpox. 

Venoms 24, 66, 78, 85, 158-160, 264-268 

Amboceptors and complements, 159, 266 ; antivenins, 
63, 267, 268 ; character of, from different snakes, 
265; cobra-lecithid, 160, 266; cytotoxins of, 265; 
endocomplements for, 159, 266; endotheliotoxin of, 
265 ; ferments of, 266 ; hemagglutinins of, 158, 265 ; 
hemolysin of, 158, 265; hemorrhagin, 159, 265; 
incubation period, 66, 267; lecithin as comple- 
ment, 159, 266 ; neurotoxin of, 158, 265 ; radium, 
effect of, 267 ; structure of cytotoxins of, 266 ; tox- 
ins of, 158; toxoids of, 265. 

Vibrio cholera. 

Acquired immunity to, 186 ; action of gastric juice on, 
39 ; active' immunity, formation of specific precipi- 
tin in, 314 ; agglutination of, by normal serum, 92 ; 
agglutination of, 315; agglutinins, 314; attenua- 
tion of, 57 ; autolytic products, vaccination with, 
313; discovery, 304; endotoxin of, 309; identifica- 
tion of, by agglutination reaction and by Pfeiffer 
experiment, 305 ; in Pfeiffer's phenomenon, 131 ; 
in stools of convalescents, 307 ; location in infected 
body, 310 ; morphology, staining properties and 
cultivation of, 304, 305 ; non-neutralization of endo- 
toxin of, by its specific bactericidal serum, 137 ; oc- 
currence of water, 307 ; resistance and viability of, 
306 ; see Cholera ; symbiosis with Ameba coli, 502 ; 
soluble toxin (?) 310; specificity of, 9; toxicity of 
culture filtrates, 309 ; toxicity of killed cultures, 309. 

Vibrio metchnikovi 33 

Virulence. 

Increase of, in the presence of other micro-organisms, 
14 ; influence of, on inflammatory reaction, 42 ; rela- 
tion of, to phagocytosis, 184 ; see different micro- 
organisms. 

Wasp poison, antitoxin for 90 

Whooping cough (pertussis) 562-566 

Contagiousness, 564, 565 ; cultural characteristics and 
pathogenicity of the influenza-like bacillus, 562 
563 ; immunity and susceptibility, 565 : influenza- 
like bacillus in, 562 ; influenza-like bacillus, rela- 
tion to whooping cough, 564 ; Micrococcus catar- 
rhalis in, 383 ; micro-organisms in, 562 ; prophyl- 
axis, 565 ; pseudo-influenza bacilli in, 395 ; serum 
therapy, 565 ; virus, dissemination of, 564. 



INDEX. 599 

PAGE. 

"Water-borne" epidemics ; cholera, dvsenterv. tvphoid. 

271, 292, 30S 

Welch, hypothesis of 567 

Widal reaction 92, 111 

See Agglutination. 
Wool-sorters' disease ; see Anthrax. 
Wright's method of vaccination. 

Staphylococcus infections, 381 ; tvphoid fever, 279. 
280. 

Yellow fever 10, 529-538 

Acclimatization, question of, 537 ; altitude and mois- 
ture, relation to, 533 ; Bacillus icteroidcs in, 530, 
531 ; cold, relation to, 533 ; epidemiology, 533 ; fo- 
rnixes. 532, 533 ; immunity acquired, 532, 538 ; 
importation by ships, 536 ; incubation period, 532 ; 
mosquito theory of, 530; see also Stegomyia fasei- 
ata ; non-contagiousness of, 533; occurrence, 529: 
prophylaxis and quarantine of, 533, 534, 536, 537 ; 
virus,' filterability of. 532 : virus, resistance of. 
536 ; serum therapy, 538 ; susceptibility to, 537. 

Zone, contagious 2, 3 

Zooprecipitins 120 

Zootoxins 268 

Zivisclienkoruer, synonyms for 148 

Zymotoxic groups 108 



600 






INDEX. 

CORRECTIONS. 



Page 8, 14th line from bottom : instead of "Strong," read 
"Musgrave and Clegg." 

Page 12, 4th line from top : instead of "Unstained ability," 
read "Unstainability." 

Page 27 : between the 12th and 13th lines from top a line 
is omitted. It should read : "Other students, especially 
Pasteur and Koch, soon took up the study of anthrax," etc. ; 
the 13th line is repeated. 

Page 57, 14th line from bottom : instead of "varioloid," 
read "variolata inoculata." 

Page 61, 4th line from top : instead of "poisons," read 
"opsonins." 

Page 85, 18th line from bottom : instead of "Part II, 
Chapter III," read "pages 158-160." 

Page 85, 4th line from bottom : instead of "equaled," read 
"equalled." 

Page 107, 13th line from bottom : instead of "flagellar" 
read "flagella." 

Page 158, footnote: instead of "Chapter III," read "page 
264." 

Page 181, 3rd line from bottom : instead of "phenomena" 
read "phenomenon." 

Page 206, 4th line from top : instead of "crawfish," read 
"spider-crab." 

Page 217 : instead of "opsinogenous," read "opsonigenous." 

Page 231, 9th line' from bottom : instead of "simulating." 
read "stimulating." 

Page 264 : The description of the poison fangs of snakes 
applies to the chief poisonous snakes of North America, 
which are "pit vipers" ; another class of poisonous snakes, 
among which are included the cobra, and tho coral snake" of 
North America, possess immovable poison fangs. 

Page 413, 3rd line from bottom : instead of "toxins of 
tuberculins," read "toxins or tuberculins." 

Page 485, 5th line from bottom : instead of "Nepreu," 
read "Nepveu." 

Page 485, 2d line from bottom, and page 490, 8th line 
from bottom : instead of "7'. neprevi" read "T. nepveui." 

Page 511, 14th line from bottom : instead of "microscopic," 
read "ultramicroscopic." 



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